Failed to authenticate on SMTP server with username "... using 2 possible authenticators in Laravel

I was able to send mail (ordering process) a few months ago on my website and then today, I got an error message like that on Laravel. I use mailgun 0$ per month plan. I tried to register a new domain today for another website mailing process on Mailgun. Please help me if you ever faced one like that. It was okay till last month and then I found out today. I didn't edit anything on my hosting for sure. : (

My .env file looks like this.

MAIL_DRIVER=smtp
MAIL_HOST=smtp.mailgun.org
MAIL_PORT=587
MAIL_USERNAME=mailaddress
MAIL_PASSWORD=passwords

via Chebli Mohamed