Not receiving SOME email

I have recently migrated to Zoho, and I'm using my own domain to manage emails. Currently I am using the free service. Given my experience to date I am not likely to upgrade as I was planning.

My problem is that since a few days ago I'm not receiving email from some senders. Not all. Most email gets through. At first, all messages were received in my inbox, but suddenly stopped and I haven't changed any setting. I have verified that I can not receive emails from @mercadolibre.com, @mercadolibre.cl, @mercadolibre.com.ar and @amazon.com. All email is downloaded to my desktop every five minutes using Thunderbird. It is not stored in my Zoho inbox unless I'm away from my desktop which is never more than a day. Therefore the problem is not exceeding the size of the inbox. I have checked the spam folder at Zoho which is always empty, and the spam folder within Outlook which has been abundantly full since I switched to Zoho. What could be preventing only some of my email from arriving?

Trying to restore previous functionality, I've checked into cPanel the Mail Administration > Spamcontrol settings looking for the origin of the problem. I've Whitelisted all the mentioned domains and verified that nothing is listed into the Blacklist. Also, at the Quarantine, added all domains in the Excluded Domain List and checked no emails are into the Quarantine Messages folder.

I've checked the Mail Logs looking for messages from those domains in the last 4 days and I can't found any.

Looking forward to finally receiving a response.

Thank you,
Dennis