Power meter showing half the expected watts


My left-only crank power meter (Watteam Powerbeat S3) shows half of the watts that it should do when I use it in Zwift. If I am sitting at the ‘connect sensors’ screen I can see that my Wahoo Kickr Snap shows e.g. 200W and the Powerbeat shows 100W at the same time.

Does anybody know how to fix this? Is there a setting to say that this is ‘left only’ power?

(I found this old forum thread Generic 2x power setting for powermeters that read 1/2 but it looks like it just got archived without a solution)