Knowing each DSP is QC 5 times on the bench before any shipments, the likelihood of a hardware failure is actually extremely low. Based on experience, what's however more likely is a DSP configuration of the plugin that isn't matching your application. :-)
Two things to always check: a) Routing of input to output (see manual if you don't know how to use a router) b) Output crossover configuration. By default, most plugins are configured for a 2way speaker. Please check your outputs crossover as per the manual to make sure you have the correct setup. e.g. subwoofer need to use LPF, full shouldn't use any filtering, tweeters should use HPF.