Hey Rosie! Sorry you’re having trouble - Is the redirect working for you? (i.e. if you share it in the way you hope your client can - Can you see what you’d expect them to see?)
If so, Can you perhaps ask your client a few clarifying questions:
What is the error they are getting?
Are they able to log-into Airtable otherwise?
Do they have any software installed that might prevent a successful connection (e.g. Firewall etc)