There could be various reasons why you are unable to proceed with payment. You may follow the steps below to troubleshoot:
If you are using cellular network (e.g. 3G, 4G or 5G) ensure that you are in an area with strong network.
If you are using your home Wi-Fi, ensure you are within your router's signal coverage, VPN servers or the firewalls are functioning as they should. Home routers, consumer VPNs or firewalls may at times fail to function properly and require a reboot or completely removing it from the power source then powering it up again after several minutes.
If you are at your workplace and connected to your company's Wi-Fi, try switching to your cellular network instead. Many companies have strict IT protocols and they differ between companies. These protocols may restrict your access to certain services.