I have QGIS 3.10.13 LTR installed with the stand alone installer on a Windows 10 machine. In this machine I have also a QGIS 3.16.2 OSGeo installation. I can work perfectly with GRASS in my OSGeo4W install. Nevertheless, I am unable to work with any grass tool in 3.10 (r.reclass, for instance). The dialog box opens, I can fill the information required but processing takes almost no time and I have no output. It is the same situation as described here:
But I have no success on the solution of the problem as exposed at the end of the entry (which is closed also).
QGIS 3.10 log message states that:
2021-01-13T11:21:53 WARNING Failed to load C:/PROGRA~1/QGIS3~1.10/apps/qgis-ltr/plugins/grassplugin7.dll (Reason: Cannot load library C:\PROGRA~1\QGIS3~1.10\apps\qgis-ltr\plugins\grassplugin7.dll: No se puede encontrar el módulo especificado.)
2021-01-13T11:21:53 WARNING Failed to load C:/PROGRA~1/QGIS3~1.10/apps/qgis-ltr/plugins/grassprovider7.dll (Reason: Cannot load library C:\PROGRA~1\QGIS3~1.10\apps\qgis-ltr\plugins\grassprovider7.dll: No se puede encontrar el módulo especificado.)
2021-01-13T11:21:53 WARNING Failed to load C:/PROGRA~1/QGIS3~1.10/apps/qgis-ltr/plugins/grassrasterprovider7.dll (Reason: Cannot load library C:\PROGRA~1\QGIS3~1.10\apps\qgis-ltr\plugins\grassrasterprovider7.dll: No se puede encontrar el módulo especificado.)
Nevertheless, the dlls are present in the directories mentioned on the log message (no se puede encontrar = can not find).
Another piece of information. About a year ago I was having problems running grass and I emplemented the solution by ewolf in this question GRASS not working with QGIS 3.6, with involves defining a path environment variable in Win 10.
How can I fix this?