Affected are both, Gog galaxy and Gog in browser.
My wishlist is grayed, I cannot add or remove titles from wishlist.In the app, wishlist count is 0, even if in the browser I see 27.Anybody had that issue? And fix for that?

One thing that you may try is to visit (with your preferred web browser) one of your wishlisted game pages (such as: Serin Fate), and simply attempt to (temporarily) un-wishlist it by clicking upon the [<3 Dodane do listy życzeń] / [<3 Wishlisted] area (underneath [Kup teraz] / [Buy now]).

Afterwards, visit your wishlist page, in order to determine if the list can be interacted with, and (hopefully) confirm that the aforementioned game was truly removed (there is a possibility that the removal might 'correct' the saved wishlist data).

Note: I have not encountered this issue (but, have tested the adding and removal of games, prior to replying to your post), and only use the web site interface.

Its weird.
On the Serin Fate page I see game like it is not on my wishlist. When I try to add again, It is flashing for split second proper state and I again have ability to add it on wishlist. Like it would unwishlist itself automatically.
Still I cannot remove it from wishlist, but that game alone is not grayed anymore in app, still grayed in web.
And still, I cannot add new games to wishlist.
I also tried solution from other topic, adding game from my shopping cart, but this also does not work.

In a similar vein as the post by Ice_Mage, does visiting https://www.gog.com/user/wishlist/add/2108847100 add the upcoming Empire of the Ants game to your wishlist? You can, conversely, remove it with this.

If the game was not added, though extreme, you could try to remove all wishlisted games:

Remove - Add -- Serin Fate
Remove - Add -- Dream Tactics
Remove - Add -- Dream Engines: Nomad Cities
Remove - Add -- The Dwarves
Remove - Add -- Disciples: Liberation - GOG Edition
Remove - Add -- Geneforge 2 - Infestation
Remove - Add -- The Temple of Elemental Evil
Remove - Add -- Children of Zodiarcs
Remove - Add -- CrossCode
Remove - Add -- Dead Cells OST
Remove - Add -- Dead Cells: Fatal Falls
Remove - Add -- Dead Cells: The Queen and the Sea
Remove - Add -- Dead Cells: Return to Castlevania
Remove - Add -- Potion Permit
Remove - Add -- Warcraft I and II Bundle
Remove - Add -- Spellcaster University
Remove - Add -- Timberborn
Remove - Add -- Ocean's Heart
Remove - Add -- Frostpunk: On The Edge
Remove - Add -- One Step From Eden
Remove - Add -- Metro Exodus - Gold Edition
Remove - Add -- Warlords Battlecry 3
Remove - Add -- Warlords III: Darklords Rising
Remove - Add -- Arcanum: Of Steamworks and Magick Obscura
Remove - Add -- Icewind Dale 2 Complete
Remove - Add -- Icewind Dale: Enhanced Edition
Remove - Add -- Neverwinter Nights 2 Complete

If you did indeed proceed with removing all games, please post the contents of https://www.gog.com/user/wishlist.json -- unless you had previously wishlisted games that have since had their product pages made inaccessible by GOG, the file should be devoid of product IDs.

Its weird, but after using your json urls for the Empire of the Ants, it looks like it restarted my wishlist, and after app restart it also reactivated my wishlist counter. Thanks a lot! With that I dont need to use that method for other games.

I will save info that you provided for me, just in case in future issues. Thanks again!

That is great to learn/read! (^_^) I am sincerely delighted (as well as relieved) that you are no longer burdened with a malfunctioning wishlist. Hopefully, for you (at the very least), there will not be a repeat of the previous set of unfortunate circumstances.

A related note: It would be quite agreeable if GOG were to introduce a bare, single-page user control panel of sorts (HTML+CSS) which would enable customers to manually-refresh specific types of seemingly-corrupted account data (beyond the effects offered by navigating to https://www.gog.com/user/refresh and/or https://www.gog.com/account/refresh). Not only would such an addition be helpful for situations such as this, but, it also may save their support staff a decent amount of time. Though, realistically, I believe that I am merely indulging in a never-to-be-satisfied fantasy.