After some more searching I've figured out that for some reason, ESXi thinks the datastores are snapshots of their fomer selves. As a rseult, once it mounts on one host in the datacenter it won't mount on any other hosts.
I used these insturctions How to force to mount a datastore with vSphere without resignature | blog.festag.de to force-mount the datastores.
1. Log in as root to the ESX host which cannot mount the datastore using an SSH client.
2. Run the command:
esxcfg-volume -l
The results appear similar to:
VMFS3 UUID/label: 4b057ec3-6bd10428-b37c-005056ab552a/ TestDS
Can mount: Yes
Can resignature: Yes
Extent name: naa.6000eb391530aa26000000000000130c:1 range: 0 – 1791 (MB)
Record the UUID portion of the output. In the above example the UUID is 4b057ec3-6bd10428-b37c-005056ab552a.
Note: The Can mount value must be Yes to proceed with this workaround.
3. Run the command:
esxcfg-volume -M <UUID>
Where the <UUID> is the value recorded in step 3.
This looks like a good short term solution, but a longer term fix will involve taking the datastore offline and re-signaturing it.