There was an error issue

Hi,
as from last week I get the message: There was an error trying to send your message. Please try again later.
checked with the server and they don’t see anything wrong.
ver: 5.4.1
php ver: 7.4.20
wordpress ver: 5.7.2
all plugins are up to date.
I installed an smtp plugin and set it up to my email account.
still when I’m trying to send an email from one of my forms it gives the same error.
I sent a test mail from the smtp plugin itself and it reached.
the smtp plugin called Post SMTP and it says that it suitable to contact form 7

The page I need help with: [log in to see the link]