After many days of troubleshooting with NetApp, the ticket was escalated to a Senior level where it finally found solution: the intra-cluster replication had stopped
It appeared that the problem was caused by the fact that SnapMirror inside the same cluster (intra-cluster replication) had not run since the month of May 2019. Therefore, for the time being, every time we will create a new Volume in this SVM, we will have to manually run SnapMirror command in order for the Root volume to become aware of the new volume since SnapMirror did not run update automatically. The feature is called: Load Sharing Mirror.
In the course of troubleshooting, we ran this command manually:
Cluster1::> set -privilege diag
Cluster1::>snapmirror update-ls-set -source-path cluster://svm_cifs/rootvol
After running this command, we were able to successfully access the share.
Note: We're still researching to understand how this feature is supposed to work. Is it automatically configured out of the box or should it be manually configured?
The engineer who helped figured out the issue wasn't versed on Disaster recovery. Therefore, he suggested that we open another ticket on the issue.