Hatsan Hatsan Jet 2 help

Hello I made an account for this just because I am very new to air guns with zero experience and I can’t figure out how to fix my Hatsan Jet
2. I just got it a week ago and I was really excited to try it out, but it wouldn’t keep the air I pumped in it at all when I took it out of the box to fill for the first time.

The barrel leaks air whenever I try to pump it with my hand pump I’ve confirmed it was the barrel. I’ve tried multiple methods I’ve seen on these forums from cocking it, pumping fast, tightening or loosening things, and I’m pretty sure some of the stuff is bad for the gun but I’m running out of options and it’s hard trying to look for new methods cuz I’m new to this and a lot of the acronyms or phrases for parts and techniques is all so new to me and to be honest idk what I’m doing.

If anyone can explain in lame man’s terms on what I can try to do I’ll forever appreciate it.
 
Are you using a hand pump? Are you sure you're getting a good connection on the to the gun? Most people recommend a blast with a bottle of air to set seals on the first fill of a pcp.
Yes i am using a hand pump and I’m certain it’s connected securely I’ve seen people say that’s a common issue but it’s not in my case. And I know for sure it’s not the pump at all cuz I used the pressure plug thingy on the pump to see if it can produce 4500 and it’s does. I will definitely try the bottle thing tho thanks.
 
Did you cock it before filling? If not Cock it and try again. If there is no air in the cylinder and the hammer is forward it could be putting pressure on the valve and holding it open enough for air to leak out the barrel. By cocking it, you are removing any chance the hammer could be holding the valve open.
Yes I have cocked it all the way back and it is still letting air out when I pump but thanks for the response.