I’m trying to buy tickets online to a variety of Krakow museums. But I can’t get any of the charges to go through. I have tried two different credit cards, a debit card, Google pay and have used my phone, desktop and laptop. Has anyone else had similar issues? I messaged one of my CC companies, but have not heard back yet.
You've tried everything I would have suggested. Perhaps your credit card company will have an explanation and a resolution.
The only tickets I bought in advance of my 2018 trip to Krakow (and doing so is necessary) were for the Schindler Factory and Auschwitz. It's possible that at least some of the places you're concerned about will have plenty of walk-up tickets available for immediate entry.