Unfortunately, there's nothing useful you can do with that device.
The PA-2000 series is End of Sale as of 2015, and will be End of Life in about a year.
Because of that EoS status, you won't be able to purchase a support contract or get any licenses for it. The Secondary Market Policy has the details.
Your best bet for on-the-cheap learning is a cloud license (AWS, Azure, etc.), a lab license on a VM (talk to your account team), or a PA-220.
You just plug it in and it boots. Since yours is stuck on an error when you try, there's literally nothing more you can do.
You also won't be able to get support on it, you can't run traffic through it, and you can't get the dynamic updates (apps, threats, etc.).
AWS is something like $1/hour if you just want to play with a firewall. But that 2020 is really just e-waste at this point.
Not sure what you paid for it, but you had probably been better off indeed with buying a recent PA220. Even it it did work, if I remember well how it worked (very very slow)...that PA2020 would have rendered you bald with in 2.47 days.
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