Getting Message: There was a problem while sending the test email.

Replies: 0

I am getting the message “There was a problem while sending the test email.” I got the message when I sent a test email. I am using Sendinblue SMPT. Here is the message in the error log. Please I need your assistance urgently.

Versions:
WordPress: 5.8
WordPress MS: No
PHP: 7.4.22
WP Mail SMTP: 3.0.3

Params:
Mailer: sendinblue
Constants: No
API Key: Yes

Debug:
Email Source: WP Mail SMTP
Mailer: Sendinblue
[unauthorized]: Key not found