All sorted now. Issue was with the initiators on the ME4024. Some hadn't been discovered correctly. I deleted the incorrect initiators, disconnecting the SAS cables first then reconnecting after. Also one of the ESXi hosts had to be rebooted with the SAS cables disconnected as it seemed to have mixed up some of the ports, which was fixed by the reboot.
I'm having some problems setting up an ME4024 with a couple of VMware ESXi hosts (v6.7). Connectivity is via SAS, each ESXi host has two SAS cards, a single port is in use on each going to one of the controllers - so each host has a connection to each controller. On the ME4024 there is a single pool (with a performance tier), currently with a single volume. Within ESXi, it shows two devices, the volume on one HBA and an enclosure on the other HBA. The volume shows as having a single path. So I'd expect the volume (LUN) to show two paths. Also when I restart the controller attached to the HBA with the volume, it doesn't fail over and connectivity is lost.I'm guessing this isn't correct. I believe I've followed the set up correctly and can't see anything wrong. Any ideas what may be causing this?  
ME4024 & VMware Multipath