It is either the pump arm seal or the firing valve seal that has gone south. These are known common failure points in the FWB 600 series rifles and are easily addressed if you are even slightly mechanically inclined.
The seals for a rebuild are available from Canada. Look on eBay under the search term FEINWERKBAU and you should see a kit available from the seller NIKKONOS in Canada. Very trustworthy seller and I have dealt with them many times.
Examine the exploded diagram of the rifle, and view any video or tutorial that you can find dealing with teardown and reassembly to familiarize yourself with the process.
If you are not comfortable with doing it yourself, then definitely send it off to one of the 2 spots that Odoyle recommended to you. DO NOT just give up on it, the 601 will outshot any of us on this forum any day of the week. If you shoot at the Olympic level, you may find the rifle lacking, but short of that it is a definite keeper.