RDP Stopped Working - "Unable to Connect" 0x204 Error

Question

I’ve been using RDP from my iPad to my Windows Desktop for several years.

This has worked through multiple updates at both ends and, when I occasionally had connection issues, a reboot of either end (and/or my wireless hub) would usually fix things. However, I cannot seem to recover this time, and I suspect a recent update - but of course everything is regularly and largely automatically updating such that I can’t tell what precisely may have changed.

Currently, the iPad is on iPadOS 14.5.1, the RD client is at 10.2.5 (4197) and Windows Pro is at 20H2, Build 19042.964, with maintenance up to and including KB4023057

Following suggestions from other threads, I’ve tried setting up a local account (rather than relying on my Microsoft passport login), and directly logging in to Windows using a password rather than the “Hello” PIN, but these don’t fix it either.

It stopped working about 3 days ago, so I’m most interested to hear of anyone with similar very recent experience - thanks

Answer 1

Update: I have found a fix for this. Sadly, I still don’t know the root cause of the error and found the fix somewhat randomly while trying to diagnose whether the Windows machine was actually rejecting the request, or never seeing it. netstat wasn’t a great help, but on the Windows Settings network page, I tried the “diagnose” option against the wireless adapter. (It wasn’t showing any problems and, during all of this, other network activity was progressing normally, so there was no indication of an adapter problem.)

The “diagnose” process did its usual thing of assuming that there was a problem, and trying to “fix” it. I therefore don’t know everything it does/did, but it certainly included disabling and re-enabling the adapter, and it declared it “fixed”. To my surprise, RDP then worked.

Maybe the device driver had become mildly corrupted, or just left in a “failed” state - and may or may not have been as a result of some Windows Maintenance… but I can now add this to my set of fixes alongside rebooting everything.