What to do when a system administrator can't access salesforce email templates?

I have a user with the system administrator profile, and suddenly it can't see anything related to email templates in Setup/Quick Search.

The user was able to use and modify them previously (just days ago) and no changes were made in permission sets or profiles that could impact the usage. I noticed that in another sandbox from the same org that has the same profile with the same permissions is able to access the email templates functionality (I noticed that the problematic sandbox is in preview of Summer '13 while the working one is not if it makes any difference).

I also noticed that for some reason if I switch to Salesforce Classic and look for the template folders manually I can actually access and modify them, however that workaround is tedious and not practical in real world usage.

Has anyone experienced something like that previously? Or any ideas of what could be wrong with my configuration? So far I tried:

*Double check that the profile is System Administrator.
*Checked that the user has Modify All Files permission.

*Created a permission set and applied it on top of that profile with the permission requirements listed by Salesforce (Edit HTML Templates, Customise Application, Manage Public Classic Email Templates, etc).