Exhaust Tube Connection

These gaskets are usually some sort of crushable mesh which are regarded as single use but I've reused them successfully with some copper or graphite grease.
Yours look shot.
This type of thing........

https://www.ebay.co.uk/itm/25662943...7vqX273hkfVfCYHQn486AC1k8=|tkp:Bk9SR7zL4u6qZQ

 

@Stu9000 And looking at that exhaust there are gaps the gasket should cover those if you can't get the can to push on a little further. That stupid Paste is a nightmare and pathetic. I myself use silicon much better and when it comes to removing the can it is easier,