iCloud.com keeps asking me to change password

this is a recent issue- suddenly when trying to log into iCloud.com web browser (chrome and Microsoft edge) on windows 10 machines I cannot. I enter my Apple ID, then password, then do the 2 step authentication. It logs in BUT takes to a screen to change password asking for more secure one. Ever since I switched over to iphone in September 2019 I’ve been able to access the iCloud.com website in these same windows machines but not for the last few weeks suddenly. The only thing I’ve changed is getting a new iPhone in early March. That’s it. What is going on with iCloud.com to suddenly not allow me access via windows even after 2 step authentication????