It's worth the time to check the Settings menu in the Google Photos app itself to optimize how your photos are backed up -- i.e. I really dislike the
Backup quality option that will either upload pics from your phone into your online Google account as
Original quality or
Storage saver. I always choose
Original quality because I prefer to have all my photos left as is. I don't want them to be scaled down just to save storage capacity. Of course since you had that lack of space issue previously you might feel just the opposite and opt to go for more storage.
But more of an incidental matter, getting back as to why your Google Photos app isn't being automatically synced with your online Google account in the background, there could be a lot of other factors involved. Try digging deeper into your Galaxy A23's Settings menu, it could be some option the Settings that's over-riding the Google Photos app.
-- There's an
Account and backup menu that includes options that allow you to choose which apps/services to automatically sync themselves. And Samsung being Samsung, there's a matter of choosing between your Google account and and your Samsung account. Samsung includes a lot of their own branded apps that occasionally duplicate already existing Google apps, so you have to choose which one better serves your needs.
-- There's also a
Connections menu that might be part of the problem. There's a Data saver option that might be cutting off background syncing so you need to add Google Photos as an exception.
-- In the
Battery menu there are options like
Power saving and
Background usage limits that you need to look into.
There are likely to be other items to check, here's a link to the User Manual for your model:
