Issue accessing wp-admin

Hi, I have built a new WP site on a new hosting package, using a “test domain” access (https://1091777559.test.prositehosting.co.uk), as the A record needed to point at the old site on a different server. Last night I changed the A record, and this morning, using “Velvet Blues Update URLs” I have changed the site URL to the correct one (https://www.mslpro.co.uk). While the site is working fine (except for the navigation, but I was going to fix this after changing the URLs), I cannot access wp-admin using “www.mslpro.co.uk/wp-admin.php”, but I CAN still access it using “1091777559.test.prositehosting.co.uk/wp-admin.php”

What have I missed? Whats the fix? Many thanks in anticipation!!