Hi,
Well, that error message means that a plugin cancelled the creation of the order but HikaShop has no information on which plugin did it.
So what you should do is to disable the plugins you're using with HikaShop one by one to identify the one causing the problem.
The likely ones you should do first are:
- if you're using a payment plugin which isn't by default in HikaShop, try with another one like "collect on delivery" to see if it comes from the payment plugin
- if you'e developed some custom plugin integrated with HikaShop, try disabling it and see if that helps
- If you have installed extensions integrated with HikaShop, try disabling them
The issue most likely comes from a plugin from the group "hikashop" or "hikashoppayment" or "system".
Once you've identified the plugin causing the problem you can report here your findings and we should be able to tell you what to do.