Hi,
if you enable debugging in the site you should be able to get more information. As admin, login in browser and go to "Site administration > Development > Debugging" and set "Debug messages" to DEVELOPER. I recommend to leave "Display debug messages" disabled, otherwise users will see errors and warnings in the UI.
After this change, open the Moodle app and go to the "More" page (the 3 dots) > App settings > General and enable "Display debug messages" in there.
Now try opening the Dashboard or Home page again, you should now see which field is the one returning an invalid value.
Cheers,
Dani