I have just installed eM Client for Windows 10.  Have two accounts, a pop3 with BT and IMAP with Gmail.  The BT account has transferred over fine, however, the Gmail account will not accept the password and I get an error saying Servers says “[AUTHENTICATIONFAILED] Invalid credentials (Failure)”.  Can you help with this one.  The password is correct, checked within the gmail app before writing this.  Many thanks.  Graham Keeley

Usually this is because the settings are incorrect.

Go to Menu > Tools > Accounts and click on the IMAP tab for your Gmail account. Make sure that the port is 993 and the security policy is Use SSL/TLS on special port (legacy)