Code P0455 EVAP leak, where is the Vapor Canister vent valve solenoid located?

Car sat for two years before I bought it and brought it back to road worthy. Had many issues and codes that I worked on and solved. Passed inspection about a month ago and then a couple weeks later would get a tighten gas cap message then the check engine light a few miles after. Already had replaced the purge valve. Already tried another gas cap (swapped it with my other Buick). So now I want to know where to find the Vapor Canister vent valve solenoid and how to get to it, and where to find the fuel tank pressure sensor (and how to get to it). I found a video on changing the fuel pump (Impala), and expected to see it on the top of the fuel pump unit, but didn't. So I still have no clue where it is, but I tried.