Hi @Ryan Kielar
I'm glad that you were able to resolve your issue and thank you for posting your solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others ", I'll repost your solution in case you'd like to "Accept " the answer.
Issue:
Setting up our first Cloud Sync configuration and trying to change the "Accidental deletion threshold" from the default 500 to 5. After changing the value, I see a notification that "Properties are being updated...", but it never completes.
Solution:
Conditional Access policies in EntraID were blocking communication from the Cloud Sync service account.
If you have any other questions or are still running into more issues, please let me know. Thank you again for your time and patience throughout this issue.
Please remember to "Accept Answer" if any answer/reply helped, so that others in the community facing similar issues can easily find the solution.