Easy WP SMTP problems

Hi

I've been using Easy WP SMTP for mailing function, with no problems up until now.

For some reason from today it's stopped working, giving me an authentication problem.

It's happening across all my sites, where it used to work fine. I use my GSuite account / SMTP server, and I haven't changed the login details, double checked and they are fine.

Any ideas why this would start failing now?

Thanks, Neil.