Custom related list Button or Link URL is not working in partner portal?

I have created custom button with content source is URL called "New Employee" on employee object and it is related with both account and contact objects via lookup relation. If i click on "New Employee" button on employee related list under Account detail page, working fine in both salesforce classic and lightning experience but not in partner portal.

{!URLFOR($Site.Prefix +'/a07/e?CF00N80000008cGU9={!Account.Name}&CF00N80000008cGU9_lkid={!Account.Id}&CF00N80000008cGUG={!Contact.Name}&CF00N80000008cGUG_lkid={!Contact.Id}&retURL=%2Fa07%2Fo')}