Lightroom Classic Not Synced up with the rest of lightroom ecosystem

If none of that helps

Contact Adobe. This via a Chat. Before doing so, prepare your notes and information ahead of time as to be more efficient in communicating. Your info that you have posted in your Discussion is a start for the description, and probably have a copy of your LrC /Help/System Info/ as a text document on hand, so that you can paste or attach that into the chat. 

To accomplish the Chat, bring up an Adobe webpage, and click on the Chat button. (see image below) This will start a Chat. At first the Chat will be with a chatbot, Typing “Agent” into the chat text field will bypass the initial chatbot. If an agent does not enter the chat then be assertive in requesting an actual Adobe Tech join in the chat.

In the Chat include (as mentioned above) a description of the issue, and probably your System Info. And include a link to your discussion.

You may want to ask for a phone call.

And please keep notes so that you can share them in your post for others to see.

For example, bring up:

https://helpx.adobe.com/contact.html

and click on the Chat button, typically found in bottom right corner

"So I've had no problems until recently"

Any suggestions to know what might have changed? An upgrade, etc?

"with lightroom classic syncing up with lightroom mobile so that I can easily review and download pictures to my phone."

Do you know that Lr-Classic only syncs proxy (aka Smart Previews) UP to the Cloud? So you won't have 'full-size' images in the Cloud. Although photos that you do sync from Lr-Classic should be showing in Lightroom-Mobile (if confirmed you are signing in with the same user credentials).

"Now it seems that my lightroom mobile and web are synced up but anything I do in Classic will not sync to those two."

Basically Classic (in its early days) was not designed to 'sync'. "Anything you do in Classic" will not sync to the Cloud unless an edited photo is in a Standard Collection that is marked to sync, and Sync is turned on in the Cloud icon.

"For example if I edit or make a new collection on lightroom web It will sync and show on my lightroom mobile but not to classic. I just want to be able to see my Classic collections on mobile."

You should be seeing your synced Classic (standard) collections showing in the mobile apps as 'Albums'.

You should be seeing Albums that you create in Lightroom-Mobile apps as Collections in Classic.

My test just now- Created a new Album in Lr-Desktop (Cloud version), added 4 photos.

A minute later- I see the 4 photos in a Collection in Classic, grouped under a Collection Set- 'From Lightroom':

Things Ive tried:
-Reinstalling all apps
-Deleting/Renaming the Sync.lrdata file.
-Rebuilding Sync Data

• Reinstalling the apps rarely fixes anything,  I cannot remember just exactly why that may help. I cannot remember the last time that did help. Also, as so many many members post v13.3 have had sync nightmares, I would think Adobe would reply if that was the solution.
• Deleting the sync.lrdata apparently post v13.3 does not help, and apparently is to be avoided (see link below)
• Rebuilding sync data, ditto

Following is now a bit dated (some update comments do exist in it), but see:

• https://www.lightroomqueen.com/troubleshoot-sync-with-classic/

In that link, letting LrC run overnight is mentioned, have you attempted that? Make sure LrC is set to prevent system from going to sleep during sync. That in LrC /Preferences/Lightroom Sync/Options/  Oh, and probably a Windows OS setting to prevent sleep as well.

Also see:

• https://helpx.adobe.com/lightroom-classic/kb/sync-faq.html