Error when creating extent: zvol does not exist

[Mike-]

Hey guys,

I have some new system on which we installed FreeNas-11.3-U5. Systems specs are: Intel(R) Xeon(R) Gold 5222 CPU @ 3.80GHz, 256Gb RAM, 24x 3,5TB SSDs
I created a storage pool Raidz2, created 2zvols and when I try to setup the iSCSI sharing, creating extent fails with Zvol /storagepool/zvolname does not exist. I can select the zvol from dropdown list but I get this error.
Any ideas?

 

[anodos]

Just FYI, FreeNAS 11.3-U5 is EOL.