Hi,
I wasn't noticed of this thread (Don't hesitate to use the HikaMarket forum section for your HikaMarket questions).
As we discussed by email, the plugin "vendor group after purchase" have some direct call to HikaMarket without a verification that HikaMarket is well loaded. It will be fixed in the next build.
Thanks for the report.
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.