Not receiving emails from specific domain

Not receiving emails from specific domain

I'm using a service called webworksheet.com to have employees email a completed web form to their manager.

The source email is submit@webworksheet.com and the destination email account is in the domain atpsystemsav.com

I am able to receive emails in the account on atpsystemsav.com from all other sources I have tested except from webworksheet.com

If I configure the form to send to emails in other domains including google (gmail.com) the emails make it through just fine no problems at all.

I contacted webworksheet support and they say that from their end after reviewing their activity logs they are not getting any error messages for my form email sends be it to the account in atpsystemsav.com or other accounts I have tried.
Their suggestion is that the problem must be with Zoho.
webworksheet.com email service is hosted on godaddy.

Funny thing is this exact web form worked just fine sending to the account in atpsystemsav.com up till 17-March then after that it seems to have been broken. I have not made any changes to the form since then and according to webworksheet neither have they at least as far as their email setup is concerned.

Assistance from Zoho support to get this resolved would be much appreciated. Need this working ASAP.

Thanks in advance