Actually, I got it working now! I tried it in Edge since I was running out of options.
I can confirm that adding a credit card does not work in Firefox.
My current credit card is expiring so I want to add a new one.
I go through the whole process and then approve on the FNB app but then on the website it gives the following json error:
{"response":{"rmsg":"Bad Request"}}
I contacted Afrihost support last week and they said they will report it...