iCloud email not working for a week , apple not able to sort out problem for a week

In the discussion you wrote - the issue is it stays cannot connect to server on iPhone and iPad

on Mac account error .

First use personal hotspot in iPhone and monitor the issue persists or not https://support.apple.com/en-us/HT204023

Possibility of router is incorrectly set up or corrupted , sometimes a slight cut in cables or you internet service provider server is down are the reasons see some articles https://support.apple.com/en-in/guide/mac-help/mchlp2414/10.15/mac/10.15

https://support.apple.com/en-in/guide/mac-help/mh11395/10.15/mac/10.15

For Mac - https://support.apple.com/en-gb/HT202068

The article is old still the concepts are used https://support.apple.com/en-in/HT202222

Emails will respond when connectivity works .

Were you already in touch with Apple Support? Have you already reviewed -- Get help using iCloud Mail - Apple Support?