iPhone iCloud Services

Why is my iPhone saying that some services are not available and that i need to sign back into my iCloud account, and when i do the phone hangs with "connection" progress wheel?

It's an iPhone 11 running iOS 14.4.2

In the Techzillo article, https://techzillo.com/update-apple-id-settings/ which is linked to on https://discussions.apple.com/thread/251369204?login=true "Apple recommends that you use the same Apple ID for all the different Apple services in order to avoid confusion."

That's all well said and done, however what happens to users who, through no fault of their own, have 2 apple ID's, one for iTunes purchases and a second for iCloud services. iTunes (January 9, 2001) predates iCloud services (October 12. 2011) by 10 years. On https://support.apple.com/en-gb/HT204053 Apple states "If you have multiple Apple IDs, you can't merge them. Not sure if this information was made available when long time users created their second Apple ID when iCloud became available. In any event, is anyone else experiencing this issue?