I know this is not a Node-Red issue per se, but I'm sure some are interested.
A few weeks ago I updated my pi4, which had a working v1.8.6 influxdb. Not until today, did I try to access it via Grafana only to be greeted by this error 'InfluxDB Error: Bad Gateway' after some RPi CLI I find Influx is not running, after an hour of reading online, trying the CHMOD fix (did not work), uninstalling directly installing later versions from v1.8.7 through to latest version; still I got the same error:
So I found this link with the old 'working version' of Influxdb v 1.8.6 which I used to re-install all worked perfect
Check your OS version (32-64bit) (armhf works for RPi4 32bit OS)