Egor, thank you for the information regarding the behavior of the saved files. That makes sense, and gives me an insight into why the issue cropped up again on a version of Illustrator that supposedly corrected the error. After fixing the type, and saving the file with 28.7.2, I have not encountered the issue again in the past week. :)

Mike, this is exactly the case. Files saved from the broken versions do not get automatically updated when these get read with a newer build — this behavior helps users to ahve the data exactly they designed it, in cases some reflows due to the core changes of text engine. In this case they can outline the result they liked at least, and have it consistent with the original intention. But in case of this error this behavior backfires. We have to make any change into a text to make it re-render — and this is what you do when assign a new color. It’d be enough to move them back and force at the same distance to trigger it.
Please try it, resave the document (in case it looks as intended), and see if the issue returns. Comment back in any case!

This insidious issue has been bothering me intermittently lately. I have been using version 28.5, and when I came here looking for help I was pleased to see an "answer" that v 28.6 fixed the issue. Well, it didn't. I just updated to 28.7.2 and it persists. (I cannot update to the newest v29 for work-related reasons. I use a plugin that is still not compatible with v 29). 

I created a video demonstrating the problem. Here is a link to view it on YouTube:
https://youtu.be/8aEUd7cB8IQ

Here is what I demonstrate in the video:

1. I open up a file. On one of the type layers, all my street labels that are text-on-path are not visible. 
2. I select all the type objects on that layer, then change their color to magenta.

3. I undo the color change and suddenly the labels look as they should. 

Is this the same issue everyone else in this thread has?

Is it possible that the issue persists in version 28.7.2 because the file was previously saved with 28.5?

ベータ版を試してみました。
最初はうまくいくのですが、２回目以降はボードの外に移動してしまいました。
しかし、ベータ版で保存し直したら、２回目以降もアウトライン化できました。

Has this issue been fixed?

Illustrator 2024(v28.5)パス上文字をアウトライン化した際に文字が消える

1. Illustrator 2024(v28.5)
2. パス上文字を選択し、アウトラインを選択
3. 文字のアウトライン化
4. 選択していた文字が消えてしまった

I'm working with some artwork having some text on path objects, when i save it as new pdf file the text will disappear and it has been caused many problem to me.
i've tried to re-install, install some lower versions but it still didn't help anything at all.
I'm using AI Desktop 28.5 - Window 10 version 22H2 (OS Build 19045.4651)
Adobe ID is company account.
Plz help to advise what's wrong with my AI and what should i do to fix it asap, thanks!
Have a look at my attached files below

AIと書き出し設定のサンプルデータを添付します。
AIデータは拡張子をpdfにしております。
ご確認ください。

環境
Mac OS 12.6　illutrator 28.5
再現方法
必ず全てのパス上文字が消えるわけではなく、特定の場所のパス上文字は解像度を150dpiだとOKで300dpiにすると再現したりします。
会社内で多数この現象が置きており早急な対応をお願いします。
CC2023（27.9.4）では問題が置きていないので、現状はCC2023にて対応をしています。

Here is away to recreate the problem (as partially described by vaccarolim in a forum post):
1 create a new file and make an oval
2 click on it with text on path tool (leave the default Myriad text)
3 save the file on the desktop
4 close and reopen the file
5 export the artboard 1 as PNG at 300 dpi on the desktop
(in the PNG file the text is invisible)
6 choose Overprint Preview in view menu the text is now invisible
7 if you uncheck Overprint Preview, the text remains invisible.
8 Select the text oval and nudge with an arrow key, the text becomes visible
9 Skip step 8 and, with the text oval selected, choose Type > Create Outlines.
The text becomes visible, but you need to zoom all the way out to see it scattered in a corner of the canvas.

This problem still exists in Illustrator 28.5 on Mac. It is very insidious as you may not realize that is has happened!

When using Export as JPG or PNG (didn't try others) in Version 28.5, all instances of type on a path were either jumbled or did not show up in the exported images (used artboards). Opened the file in a previous version of Illustrator (ver 27.9.4) and it exported all images (both filetypes, artboards) correctly.

同様のことが起きています。
OS Mac 13.6.3　Illustrator 28.5

以下の手順で発生します。
1.パス上テキストを作る
2.一旦保存し、イラレデータを閉じる。
3.イラレデータを開き、書き出しをする（ファイル→書き出し→書き出し形式　PNGとJPGで発生を確認済）
4.表示→アウトライン表示にする。
5.パスは残っているがテキストがアートボードのはるか外に吹っ飛んでいる（消えたように見える）

こちらの事象に似ているかなと思いました。
【解消済】Illustrator 2023(v27.7)パス上文字をアウトライン化した際に文字が消える事象について
https://community.adobe.com/t5/illustrator%E3%83%95%E3%82%A9%E3%83%BC%E3%83%A9%E3%83%A0-discussions/%E8%A7%A3%E6%B6%88%E6%B8%88-illustrator-2023-v27-7-%E3%83%91%E3%82%B9%E4%B8%8A%E6%96%87%E5%AD%97%E3%82%92%E3%82%A2%E3%82%A6%E3%83%88%E3%83%A9%E3%82%A4%E3%83%B3%E5%8C%96%E3%81%97%E3%81%9F%E9%9A%9B%E3%81%AB%E6%96%87%E5%AD%97%E3%81%8C%E6%B6%88%E3%81%88%E3%82%8B%E4%BA%8B%E8%B1%A1%E3%81%AB%E3%81%A4%E3%81%84%E3%81%A6/td-p/13919494?profile.language=ja

現状はver28.4.1に戻すことで回避していますが、この不具合は業務に支障が出るため、このままではバージョンを上げることができません。大変困っています。

我也遇到了相同的问题，在Illustrator 28.5中。
当我用文字工具（T）再次点击路径时，文字又回到了路径上。

When using type on a path and I reopen a file, types on a path render all over the place.

See video of me changing it back. Type disappears out of view and spread ALL OVER the document.

Illustrator 28.4.1
MacOS Big Sur 11.7.10

Illustrator 28.3
OS 13.6.6
Mac mini Apple M1

曲線パス上のテキストを文字アウトラインがしたところ、
アートボードの外に移動してしまった。
気づかずに入稿してしまったので、早急に直して欲しい。

お使いのデバイス情報を教えてくださると助かります。よろしくお願いします。

Hey there's a chance that rotating the text brings it back! took 3x longer than it should have but i got it done!

Does not happen for me, it seems... Perhaps it’s file or machine specific?
Please provide a test file and record a short video that demonstrates the steps.