Cannot register Azure Integration Runtime

Question

Hello,

I am trying to register a self hosted Azure integration runtime. This used to work before, but suddenly the existing runtime could not connect anymore.

I already:

Reinstalled the local runtime installation
Removed integration runtime in Azure and created a new one
Regenerated keys in Azure and tried key1 and key2
Tried to install the runtime on another server
Tried to use the Express setup from the 'Edit integration runtime' page

But when I try to register I always get the following error:

In the event log I get the following error:

Failed to get service token from ADF service with key ****************** and time cost is: 0.1628846 seconds, the error code is: InvalidGatewayKey, activityId is: 445deaef-dcd5-44c9-9123-703b81b35f3f and detailed error message is Processed HTTP request failed.

at Microsoft.DataTransfer.DIAgentHost.NamedPipeControllers.NamedPipeGatewayClientController.AttachGatewayNode(String[] args)
at Microsoft.DataTransfer.DIAgentHost.NamedPipeServer.MapNamedPipeRequestToController(String requestTemplate, NamedPipeStreamString ss, NamedPipeDataContract`1 result, String temp)
at Microsoft.DataTransfer.DIAgentHost.NamedPipeServer.PipeServerThread(Object data)

So here there is mention of 'InvalidGatewayKey' and 'Processed HTTP request failed'

I couldn't find any useful information on these errors, so any help is greatly appreciated!