Hi, we have resolved this issue.
Finally, Mender needs the intermediate certificates of the CA authority within the individual certificate file in each service :
/production/keys-generated/certs/api-gateway/cert.crt
/production/keys-generated/certs/storage-proxy/cert.crt
so these files would look exactly like
/production/keys-generated/certs/server.crt
It is also advisable to download the root certificate files of your CA and include them in the server path in /etc/ssl/certs/ if they are not already there.
With this, clients can now connect perfectly to the mender server, and everything works fine.
Thanks for your help.