Authenticating DKIM record with Google Workspace

So I have a slightly convoluted set up where emails to one address are meant to forward to another. This worked until it suddenly stopped working on 1st November. My hypothesis is that this was due to increased enforcement of security around DKIM from Google. Google is relevant as the address to which emails are forwarded is a Google Workspace address.

So, I've tried to do the DKIM authentication thing in Google Workspace, but after waiting 72 hours, it still hadn't authenticated (even though the DKIM record had clearly propagated).

Any ideas? The domain is scruffyleadership.uk, in case that helps. Thanks!

Edit, additional info: I first used a 2048 bit key which had to be split, so now I've tried it with a 1024 bit key in case that solves the problem, but it hasn't helped.

Edit, Oh! The UI for DKIM authentication in Google Workspace is super confusing. Right now it says both of the following:

STATUS: Authenticating email with DKIM.

and:

You must update the DNS records for this domain.
To start authenticating email for the domain selected above, enter the following DNS TXT record into your domain provider's DNS settings page. Then click 'Start authentication'.

As far as I can tell, that means it's working AND it's not working at the same time... Is that right?

It seems Google Workspace is just stuck between “waiting for DNS” and “authenticating.” If your DKIM TXT record is correct and propagated, sometimes you just need to click “Start authentication” again in the admin console or wait a bit longer. Double‑check the selector and record format, because even a small typo will keep it from verifying.

You can dig deeper by checking https://knowledge.workspace.google.com/admin/security/set-up-dkim