Unable to mount a cifs share in Centos, and from Windows clients which are not domain joined

We have a departmental file share and using "mount.cifs" in Centos works to connect to the share. Windows clients either standalone or domain joined can access the share. Fine !! We have a Dell storage device running FluidFS. Only Windows clients which are domain joined can connect. * Non domain joined workstations give the

The specified network password is not correct

error. * The Centos machine gives

mount error(13): Permission denied

I have tried all values for the sec option in Centos. Centos extract from /var/log/messages May 19 15:33:25 backup kernel: No dialect specified on mount. Default has changed to a more secure dialect, SMB2.1 or later (e.g. SMB3), from CIFS (SMB1). To use the less secure SMB1 dialect to access old servers which do not support SMB3 (or SMB2.1) specify vers=1.0 on mount. May 19 15:33:25 backup kernel: Status code returned 0xc000006d STATUS_LOGON_FAILURE May 19 15:33:25 backup kernel: CIFS VFS: Send error in SessSetup = -13 I don't understand what's going on. Any advice is welcome. George