TZ600 Manual signature upload error: FAILED: signature import is already in progress

I am trying to manually upload signatures to firewall that is not internet connected due to security requirments.

I am following this https://www.sonicwall.com/support/knowledge-base/how-to-upload-security-services-signatures-manually-on-closed-environments/170503557074578/

When I import signatures I get this error "error: FAILED: signature import is already in progress"