Apologies for the delay in answering this post.
I completely agree if you have P1/P2 license you should be able to see sign in logs in your log analytics workspace.
We have seen similar issue in the past where after considerable delay ( 2 to 3 days ), we were able to see sign in logs in the workspace,
After reviewing the logs, worked with product group team internally to get the sign in logs ingested to the Log analytics workspace.
Let me know if you have any further questions.
Please remember to Accept Answer if answer helped, so that others in the community facing similar issues can easily find the solution.