Hello,
Here the page for the 5080 error :
www.opayo.co.uk/support/error-codes/5080...-registration-failed
SagePay are not seeing the "transaction" coming through since the request is not fully signed with your details so is not "attached" to your account.
But the network request is made and their server replies to you with that error code.
That code indicates that the content is malformed OR that the encryption password is incorrect.
Since the same version of the plugin is working on live websites, please check that your plugin instance configuration has the correct password. Please verify that it does not contains extra blank characters such as spaces.
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.