1st step in most tech matters - Log out, log back in and see if issue continues.
Next step if it continues - log out, power off your device, power on your device, log back in. (Please note - I've found the 'Restart' option on most devices is generally not the same as actually powering off and powering on when trying to clear issues).
I am currently logged in and not experiencing ads. Whenever I've noticed ads is the same time I notice I can't see pics in the posts - because I'm not logged in.
Your mileage may vary.