GROUP BY time wont work - is it issue with timestamps value in db or in the reading it? (im not sure)

got headache, it seems to be right but clearly it isnt…why?

SELECT value FROM n_franluft limit 10; gives me this…3sec interval storage…

SELECT “value” FROM “autogen”.“n_tilluft” WHERE $timeFilter gives me readings fine…

SELECT “value” FROM “autogen”.“n_tilluft” WHERE time >= now() - 1h GROUP BY time(10s) gives me error
“InfluxDB Error: GROUP BY requires at least one aggregate function”

"SELECT mean(“value”) FROM “n_tilluft” WHERE time >= now() - 3h GROUP BY time(5m) fill(null)" gives me
“InfluxDB Error: unsupported mean iterator type: *query.stringInterruptIterator”