Whilst it's true the vantage driver will backfill records generated during a WeeWX outage there are some conditions/limitations. Firstly, in
weewx.conf under
[StdArchive] option
no_catchup must either not exist or must be set to False otherwise the hardware record catchup will not be attempted (the
no_catchup option is not included in
weewx.conf for a default install so likely it will not exist on your system). Secondly, and what probably prevents most catchups occurring, is that the catchup only downloads those records that are newer/younger/more recent than the timestamp of the last good archive record in your database. Whilst your missing data may well be in the data logger it could be the you have a record in your archive that is timestamped after the logger data of interest. In this case the easiest solution is to stop WeeWX and use the
wee_device utility with --dump to dump all of the archive records stored in the logger to WeeWX. You can check the WeeWX log to see what records were downloaded during the dump.
--dump will download all stored archive records but only those not already saved in the WeeWX archive will be saved, those already in the archive will generate a duplicate key error which can be ignored.
Just for completeness there is one other situation where backfill of logged data did not occur. WeeWX v3.9.0 introduced a change whereby backfill was only attempted on startup if hardware record generation was in use. This behaviour was changed as of v3.9.1 and backfill is now attempted irrespective of whether hardware or software archive record generation is used.