0x800705B4 wraps Win32 error 1460 (ERROR_TIMEOUT) — "This operation returned because the
timeout period expired." The device sent its SCEP request (or tried to) and gave up waiting
for a response. The endpoint is reachable enough to connect, but too slow to answer — or
something between device and server is holding the request.
0x800705B4
Timeout talking to the SCEP endpoint
What it means
Common causes
NDES/SCEP server overloaded, or its issuing CA responding slowly, so requests exceed the client timeout.
The CA performs slow revocation or directory lookups server-side before issuing.
A proxy or TLS-inspection appliance holds or re-queues the SCEP POST.
Large enrolment waves (new deployment ring, mass renewal) hitting a single NDES server at once.
How to fix it
Time a manual request: measure how long the SCEP URL takes to answer from the same network. Multi-second responses point at server-side processing, not the client.
Check CPU, memory and IIS queue length on the NDES server during failure windows; scale up or add a second NDES server behind a load balancer if it is saturated.
On the CA, confirm it responds quickly to
certutil -pingfrom the NDES server; slow CA responses cascade into client timeouts.Stagger large assignments (deployment rings) so renewals do not stampede the endpoint.