Submodule problems. fatal: remote error: upload-pack

I get this error while trying to deploy my site on cloudflare.

21:25:09.987	fatal: remote error: upload-pack: not our ref 5dd5becd881228bee105861429c2a07fc0c8d837
21:25:09.987	fatal: Fetched in submodule path 'themes/DoIt', but it did not contain 5dd5becd881228bee105861429c2a07fc0c8d837. Direct fetching of that commit failed.
21:25:09.987	fatal: 
21:25:10.962	Failed: error occurred while updating repo submodules

I don’t really know how to tackle it. I found this reddit post, but I got everything updated and still throws this error.

That reddit post isn’t helpful.

Assuming that you have not modified the original theme files, uninstall and reinstall the theme.

I am following the link you provided and doing the steps, but I ge this error when trying to add again the submodule:

fatal: 'themes/DoIt' already exists in the index

I solved it by following this stackexchange question using git rm -r --cached projectfolder and then removing the directory of the theme with rm -rf themes/DoIt.

I then continue to follow the instruction from your linked, and it was all good. Thank you.