Contribute error

Hi there
we recently launched our ico and everytime someone tries to contribute it gives an error
https://wizard.oracles.org/invest?addr=0xa62eeD0A68B158Cfc93fE518F10719d8a21E45B4&networkID=1

what is the proplem ?

I thought this was very weird considering our website is getting a few thousand unique visits per day

this error comes up
TRANSACTION HAS FAILED, PLEASE RETRY

Please take a look: https://github.com/poanetwork/token-wizard/wiki/Token-Wizard-Possible-Tx-Failures