It's probable that the IP address for your PS3 changed when you installed your router. You may need to reset your devices in Serviio console - on the status tab remove all devices in the list, turn your PS3 on and press refresh - see if the PS3 is automatically detected and that the correct PS3 Profile is assigned to it (if not, manually assign it).
Although up to you, don't necessarily ignore the suggestion to convert your files to MP4 (particularly if the PS3 is your only renderer). The PS3 plays MP4's natively and you will have a better experience fast forwarding, rewinding, etc. The conversion is simple remuxing of streams from the MKV into an MP4 container and takes about the same time as a file copy. If a Windows user
my tool here can also be used - just drag your files to the Remux tab, set to change from MKV to MP4 and press Go (ps. if you dont want to set the tool to auto-start with Windows for the Sleep function, turn it off on the Settings tab).