Cannot see SMB mount

I have a customer running my app under RHEL… Everything seems to work OK except: They are using a SAN with a mounted SMBv1 volume which my app cannot “see” using code like folderitem.TrueItem(i)… Permissions are OK and it did work on a previous version of the SAN… They also tried mounting with SMB2.1 and that did not help.

Any ideas what might be wrong and how to fix?