After upgrading from an earlier ESXi 7.0 release, previously created NVMe / RDMA namespaces and datastores are no longer visible in the vSphere Client.
In the vmkernel.log, you find the following warning:
(...) WARNING: NVMFVSI:861 Invalid admin queue size 16
To work around this issue on ESXi releases before 7.0 U3f, use the attached python script to change the admin queue value in configstore:
# python ./kb_88938_script.py