I purchased the Pathfinder: Kingmaker Imperial Edition after game launch. After install, I was able to access the DLC of the Red Panda and the additional character portaits, however I could not find the signet ring/belt. I contacted GoG support and followed their advice (Verify/Repair the install). Now I do not have access to the additional character portaits ~and~ I still do not have the signet ring/belt. I am not sure if I have access to the Red Panda as I have not played the new game thru to Oleg's Trading post. (I do have a game save at Oleg's Trading Post just prior to the first bandit fight, and no, the ring/belt are not in the upstairs chest.) I'm fast approaching despair. Any one else in the same boat with me? Won't really help but sometimes it helps if you know that someone else is in the ocean with you while the boat goes down.

Ugh! Now it tells me I can't attach the screenshot! Wrong File Type!

Apparently Firefox doesn't use Javascript.

Thanks to Vipster and Illona for a work around to getting the portaits. Still no ring/belt.

Yes. Here is a discussion regarding this matter:
https://www.gog.com/forum/pathfinder_kingmaker/does_anyone_have_the_dlc_pathfinder_kingmaker_premium_digital_copy
We have come to the conclusion that the missing Premium Digital Copy DLC for Windows was fixed for Premium pre-order owners whereas Premium non-pre-order owners still cannot install/access this DLC.

Please keep in mind that you will have to manually install the Premium DLC to be able to receive the signet and belt.
You can do that in GOG Galaxy by ticking the Premium Digital Copy DLC ( if / when it becomes available on your account in DLC section at the game settings card )

As a side note - GOG is going thru some serious breakdowns at the moment (javascript related). The library cannot be accessed outside of GOG Galaxy.