I think I have found the problem ā nothing to do with moving sites around - the SSL certificate for my site expired a couple of days ago (great service from my hosting supplier ā no message or warning givenā¦..).
I used Akeeba to move from mysite.co.uk to mytestsite.co.uk. So this morning I tried again moving to another domain and I get the same problem. But this time, the first time I try to access the invoices I get a browser security warning (which, I now remember, I got before).
So I change the CB-Subs Settings > Global >PCI-DSS settings >Credit-Card Form http(s) mode from āForce HTTPS on CBSubs formsā to āKeep HTTP/HTTPS mode as isā ā and the invoices display OK. Changing this option back causes the problem to re-appear.
So the test site is now working OK ā but ideally Iād like to return to āForce HTTPS on CBSubs formsā. Hopefully getting a new certificate will sort the problem, but if not Iāll contact you again.
Please accept my apologies for the time Iāve wasted ā I guess the only benefit is that you can add this to your knowledge database ā just in case it happens again.