Cannot log on to essbase/jet page via https. Same issue for Smartview essbase

Hello all,

Recently we have upgraded EPM from 11.2.14 to 11.2.15 and later. All works ok except for the access to the /essbase/jet page via https. The page itself loads ok, but when I type in the credentials (MSAD or native, makes no difference) and click on "Sign In", then the same page appears again as if the credentials were incorrect.

Accessing the same page via http works ok and I can log on to the essbase jet page.

The same issue with the logon page happens when trying to connect to essbase from Smartview via https shared or private connections URL.