I had the same problem.
My blog https://blogpro.toutantic.net is hosted at textdrive.com.
When I try to switch my permalink to “Date and name based” I get 404 from apache.
I tried the latest functions-post.php and classes.php but the problem was still there…
blogpro is a directory under my root…
Went to Option page and modified it like this
WordPress address (URI): https://toutantic.net/blogpro
Blog address (URI): https://blogpro.toutantic.net
It works!
Just one problem left
I canno’t use the url https://blogpro.toutantic/net/wp-admin for administration I must use
https://toutantic.net/blogpro/wp-admin
