Client has stopped working

I am new here but have been a long-term user of eM Client with no problems - until yesterday.

My account is linked to a G-Mail account but yesterday afternoon eM Client stopped working, I have done all the usual shut downs and restarts to no avail.

Clicking on the red warning triangle gets the message the connection has failed due to temporary server unavailability or incorrect settings.

It is working fine on G Mail/webmail and my broadband connection is fine.

I’m not a technical person so would appreciate any assistance. Thanks