Why we are not receiving submission emails?

My form is unable to send auto res ponders or email notifications. The emails are not in the bounce list however the problem is there. This problem arises time to time therefore it needs a permanent solution. the more alarming thing for me is that the form works fine and one fine morning the problem arises. i am a premium user therefore need a premium timely support to resolve the issue. the form name is "inquiry submission for v1.0"

We're sorry for this inconvenience. We had a certain delay in email delivering recently. Your emails are not lost and they will arrive.

I tested by adding my email as a second recipient and as an autoresponder email and both were received instantly. 

Could you please check and confirm if the issue persists on your side?

Thank you!