Mpesa express is unreachable, please try again later

Hi,
Mine was working, until I tested it again today and saw this error “M-pesa express is unreachable, please try again later” when I try to make payment. After checking everything I realised the problem could be because my primary domain changed. I migrated my site to a new server and for some reason had to Swap domains. Is there any way you could help me to whitelist my new domain? I had the same problem with another plugin (WP Rocket) but I was able to delete my old domain from their dashboard, and replace with new once. But here its impossible, unless you do it from your end, or may be I purchase a new plugin with my new domain – Please help