Hello, on one of my servers, the upgrade repository works fine. The other one, it spits out an error upon apt update:
Err:6 https://apt.hestiacp.com focal InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A189E93654F0B0E5
Fetched 3,599 B in 1s (3,093 B/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://apt.hestiacp.com focal InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A189E93654F0B0E5
W: Failed to fetch https://apt.hestiacp.com/dists/focal/InRelease The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A189E93654F0B0E5
W: Some index files failed to download. They have been ignored, or old ones used instead.
Is there a way to fix this? Thank you for your time. 