Symptoms:
The ESXi host displays this message:

Shutting down firmware services...
Page allocation error: Out of resources
Failed to shutdown the boot services.
Unrecoverable error

This failure occurs due to an incompatibility between the ESXi 6.7 Update 3 bootloader and the UEFI version on certain hosts.

When the failure occurs, ESXi Hypervisor Recovery cannot roll the host back to a bootable state because Hypervisor Recovery does not have the ability to roll back the bootloader.  Hypervisor Recovery rolls back only the installed VIBs.

The issue is resolved in ESXi 6.7 EP13 (ESXi670-201911001), available at VMware Patch Download.

Workaround:
If your host is unable to boot in UEFI mode because of this issue, use one of the following workarounds to repair it:

• Use Legacy BIOS (CSM) mode
• Use an ESXi installer CD (ISO image) from an unaffected release

Legacy BIOS

1. Switch the host to legacy BIOS mode.
2. Boot ESXi.
3. Upgrade to ESXi 6.7 EP13 using your preferred method.
4. After the upgrade is complete, switch back to UEFI mode.

ESXi installer CD

1. Boot the system from an ESXi 6.7 Update 2 CD (ISO image)
2. Proceed through the install until the ESXi and VMFS Found screen
3. Select Upgrade ESXi, preserve VMFS datastore.
4. Complete the installation.
5. Boot into ESXi 6.7 Update 2.
6. Upgrade to ESXi 6.7 EP13 using your preferred method.  Perform this upgrade in a single step, directly to ESXi 6.7 EP13.  Do not upgrade in two steps, first to 6.7 Update 3 and then to 6.7 EP13.