Yesterday I was able to run the r.watershed tool multiple times without any issues, today it's failing every time with "ERROR: Raster map or group not found". I am running the same DEM with the same parameters. This is in QGIS 2.18 but I get a similar error when attempting the same in QGIS 3.
I completely uninstalled and re-installed QGIS but this did not help. Any solutions on how to fix this?
EDIT: I decided to run this in GRASS itself and there are no issues.