The issue was that I was completely unable to activate the Tezzeret Planeswalker card, as clearly shown in the attached screenshot. This is the first time I have personally encountered this error, but I have noticed that other prominent players and streamers (e.g., JustLola) were experiencing the exact same problem.

Upon restarting the game, the issue was resolved and I was able to use the card again. However, in the process of trying to fix the bug, I lost a critical amount of time, resulting in the loss of two full turns/timers (two "ropes"). This severely compromised my strategic position and final decisions on a complex battlefield, leading to a loss.