file .meta input file does not exist

Good morning
Installed emoncms on raspberry pi I use Solpilog and inserting a formula in “Post processing” gives me this error:
{“formula”: “f13 * f14”, “output”: 58, “process”: “basic_formula”}
the formula is fine !!
13.meta input file does not exist

Any help is appreciated.

OK, the 13.meta is part of the data that EmonCMS is collecting, there will be a 13.dat that matches it in the /var/opt/emoncms/phpfina folder. Have you accidentally deleted anything in that folder?
Or is the formula you’ve inserted reference a feed that does not exist? (Sorry not familiar with Solpilog)