This is a bug report carried over from UserVoice, started July 26, 2021 (I think version 15.4, PR 2021). When posted here on 1/24/23, it had 36 votes. It was one of various bugs in different versions that shared a symptom of captions not being created from a transcript. From more recent comments in this thread, I am not sure what version users are running and which of the various bugs they are experiencing.
I could not replicate the original bug, but I believe that it was fixed in the PR 2022 version.
If you comment in this thread, would you please indicate the version of PR you are using? And what particular symptom you get?
Screenshots are not carrying over from UserVoice (or at least did not so far). To see any screenshots, here is the link to UserVoice for this bug:
https://adobe-video.uservoice.com/forums/911233-premiere-pro/suggestions/43854591--create-captions-not-working?page=1&per_page=20
Edit: 5/2/23 The UserVoice posts are no longer available.
Stan