Never seen this error before. Seems to be an issue with the VTs signature verification via GPG. ospd-openvas fails to start because of the GPG issue, gvmd therefore can’t load the VT meta information from ospd-openvas and as a result the scan configs can’t be loaded because they require the VT meta information.
Could you try disabling the verification by running
echo "disable_notus_hashsum_verification = True" >> /etc/gvm/ospd-openvas.conf
(probably as _gvm user) and restart ospd-openvas (sudo systemctl restart ospd-openvas).