GOG is not letting me add games to my wishlist, whenever I try to it asks me to log in, even though I am already logged in. When I try to log out, it doesn't let me do that either and I remain logged in. It has done this on each browser I have logged in on.

Same.

Clearing cookies and cache doesn't help either.

I guess GOG doesn't care whether I wishlist games or not.

Perhaps you might ask someone @Gog to assist in your enquiry in a more formal capacity?

They are friendly. :)

edit: linkie

Perhaps try wish listing games via gog galaxy, it is in no way optimal but it might be a temp solution till the bug is fixed.

Someone in a different thread suggested the cart workaround:
Add a game to the cart, then go there and click the "move to wishlist" button.

It works for me, but honesty, why do I need to beg a company to make buying stuff from it easier? Isn't that basic business sense?

Is it also broken on other browsers for you? I wishlisted Shing, Outcast and Skyrim. Wishlisting worked fine on Chrome, Edge and Firefox v112

Wishlisting doesn't make buying easier. That's what the cart is for. :)

It ain't about buying the game, it is keeping it on a list to get later when it goes on sale. Strangely enough, it works on my iPhone.

What browser are you using? Is it out of date?

On current release fo Brave (Chromium based browser) I have had zero issues with wishlisting items.

Turns out it was purely a Win7 issue. Once I switched to Win10 everything started working again.

I just had this happen to me and found it was due to a new host of api.gog.com (since I do cname uncloaking and default do not allow content from third party sites until manually approved). This is the first thread I found about the issue so mentioning it here in case anyone else finds it. Check that you aren't somehow blocking api.gog.com.

Same problem here a couple days ago, I had to unblock gog-cdn.us-eu.map.fastly.net.