Password change in google

I’ve changed my password on google mail and I am now asked to sign in on em client and given a code to copy and paste into the application but I can’t seem to copy it or get back to the application?

One thing you can try is to remove eM Client app from your Google security settings. Close eM Client then go to https://myaccount.google.com/permissions and click on eM Client and choose Remove Access.
When you restart eM Client it should redo the 0Auth token. See if that changes anything.