Keeping searching for a solution or explanation about the missing TAGs in Onedrive website but haven't found anything yet.
I found a concern information about Sharepoint:
SharePoint Tags & Notes feature retired
https://support.microsoft.com/en-gb/office/sharepoint-tags-notes-feature-retired-77851bd5-6d5e-42fe-9bf6-d7c17eeb771f
I can not understand why Microsoft has been killing this feature overtime and in this website they offered some workaround for the lack of TAGS and comments on files.
But going back to photos, hopefully this decision (I don't know if it is new or not because I was not able to find a date on the article) will not affect Onedrive and photo TAGs.
Recently I have been investing a lot of time tagging my photos in my computer before upload to Onedrive website.
(just a side note, I'm using Directory Opus 12, where I can tag a photo or a file keeping the "Date modified" untouched, export the date modified to date taken when this field is empty or export the date taken to the date modified field when I'm pretty sure
that the date taken is the correct field - I can also add a new TAG to several photos preserving the TAGs that they already have)