Boiler not registered with gas safe

It's probably been installed by someone not on the register, I would turn it off, for safety and contact a gas engineer to come out and investigate it make it safe, I would also get into contact with who ever you bought the house from and the estate agents and make sure they cover the fees as they shouldn't be selling a house with a currently uncommissioned and potentially dangerous appliance, finally contacting gas safe register and see how they would like to proceed in regards to RIDDOR I would try find out who installed it and report them as they clearly are cowboys

Firstly your solicitor should have asked about the boiler during the purchase of the property and any problems should have come to light. And then sorted before you purchased the property. As previously said I would contact Gas Safe but also the boiler manufacturer to ask about warranties etc.

Apart from anything else surely this is an omission by your solicitor who should have checked this amongst other items Have you not got the instruction book which usually has details of checks made and who commissioned the installation This would state the installers information It could be that they just failed to notify