What happens?
Any error message?
Have you tried another device and or browser?
You might want to contact 48 support
http://www.48months.ie/help/ask-agentIn the meantime you could top up by voucher
http://community.48months.ie/t5/Most-Popular-Questions/How-do-I-top-up-Overview-of-the-top-up-paymen...Hope this helps.