I often get an error gpg: keyserver receive failed: No keyserver available. I suggest to try multiple key servers if one fails:

ha.pool.sks-keyservers.net
hkp://keyserver.ubuntu.com:80
hkp://p80.pool.sks-keyservers.net:80
pgp.mit.edu

It's really hard to understand sometimes why a key server isn't available, for example, it may be available from travisci but not available from a local machine. It could be caused by proxy services (.e.g. cloudflare) IPs being blocked by a government regulator (hello to abhorrent Roskomnadzor) which used by a key server. Besides, sometimes it just randomly happens even on travisci, so it can improve the build time.

Example script: https://github.com/wodby/alpine/blob/master/bin/gpg_verify