This page provides solution for payment expiry screen appearing early on checkout
Problem
While using blockonomics plugin for checkout, the payment screen shows expired almost instantly or it shows expired very fast. For example even if timer is 10 minutes, the screen expires in 2 minutes
Solution
The main cause of this is that your server UNIX timestamp is not correct. Since the time of start payment is recorded on server; if there is a sync problem between server and browser time it leads to issues like this. To fix this you must sync your server to correct UNIX timestmap. You can do this in various ways
On Ubuntu
You can sync time using ntpdate
sudo ntpdate -s time.nist.gov
Using CPanel
In most cpanels, you can find this option in Server Configuration > Server Time
There is no need to change timezone. You should only try to Sync Time with TimeServer