I also came across this issue today during a cube draft match. I've attached a screenshot of the issue. See I have three untapped swamps but the game would not let me cast the Liliana of the Veil that I had in hand. The screenshot was taken during my end step, but I tried to cast the card in main phase. Both by dragging it onto the battlefield and by manually clicking my swamps to tap. The game would not let me manually tap the rightmost swamp, it was like it was not there.

Happy Thursday WOTC, I’ve come across an issue twice now, once last night and one this morning that although I have untapped mana it won’t let me play certain cards. I did not take screenshots for I didn’t know that there was somewhere to submit them and I have never had to reach out before. But today for instance, I had one untapped dual land, green and blue, and it wouldn’t let me play my thirsting roots to proliferate my evolving adaptive. Which in turn would have made him a 3/3 and causing an entirely different outcome early on in said match. The game last night I didn’t mentally record any specific cards but I know it happened multiple hands in a row, preventing me from playing a few of my bigger creatures in which I just conceded. I’m not sure how many others are experiencing this but wanted to reach out and let it be known. It has only been happening since the latest update on Tuesday/Wednesday. Thank you guys for such a great game and bringing back a lapsed fan of probably 20 years and enjoying the decision!