I have the same problem and the gmail.com domain is not on the blacklist. A number of specific gmail addresses are, but not the domain/
If you don’t have any Gmail address’s or Gmail Domain setup in the eM Client Blacklist or separately in an eM Client custom Rule via “Menu / Rules”, then emails going automatically to the spam / junk folder, must be then doing that “from the Gmail mailbox end” as @Gary advised, where you will then have to go into the Junk / Spam folder online and “Mark those as Not Spam”. You Gmail mailbox will then remember that for future to keep that senders emails in the Inbox.
To dbl-check if its an eM Client rule setup automatically moving them, for a test “disable all rules”.
Then if that senders emails stay in the Inbox in future, you know its one of your rules setup. If that senders emails still automatically go to the eM Client junk / spam folder, then you know its a Gmail mailbox issue and you have to then mark them online as as Not Spam as advised.