Hi,
The error message "mismatched tags" is coming from the eWay payment platform.
You should contact directly the eWay support in order to have more details about the source of that issue.
The plugin do not have errors ; it just display what the payment gateway replied.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.