iPad pro M4 hdmi output not working with usb-c docks

Not all USB-C docks work well with iPad/iPadOS - compatibility being largely determined by the dock's internal architecture and chosen chipset.

When purchasing a USB-C dock to be used with iPad, you would be well advised to choose a dock whose manufacturer explicitly states compatibility with iPad.

As an observation, I use both a Kingston Nucleum and Apple USB-C Digital AV Multiport Adapter - each incorporating an HDMI port. Both work without issue with an iPad Pro under iPadOS 17.x/18.x.

To reiterate, not all USB-C docks work well (or consistently) with iPad/iPadOS. You would be well advised to verify that the dock manufacturer explicitly states compatibility with iPad.

Rudeness towards Contributors is not constructive to your cause. Other than offering advice or guidance, I (and others here) cannot resolve your immediate issue. If you dock has "started working again", something has changed - and is not due to a software update.

Please understand that the Apple Support Community is a user-to-user technical forum. Contributors here are all end-users, just like you. Where we are able, we offer help and share knowledge.

Other than the site Moderators, Apple neither monitor nor participate here. As such, if you intend complaints to reach Apple through these forums, you will be sadly disappointed.