Same problem here with firefox! The Splinterlands icon just keeps spinning. I thought it was a problem with the server and lost out on some legendary cards I had rented. Similarly I shifted to Brave about a day later and figured out that it worked, and am still using that, since Firefox still seems to be malfunctioning for me. Hopefully it gets squared away soon!
My favorite most enjoyable game was Wizardry! Can't count the hours I spent trawling the Proving Grounds searching for Werdna. A true classic!