Hello. Old newbe here

[Blufx]

I joined several years back, but due to a couple of crashes, repair time, and finally some lifeform lower than brown algae stole my drone. Well, I decided to give it another shot. I found a P4 standard on ebay. Seller claimed after purchased new it was flown two times, then put in storage for years. He added the batteries wouldn't charge.
Okay. I bought it. I bought two drone batteries and a controller battery. As it turned out, the controller wasn't charging. After a failed attempt at reflowing a chip on the motherboard, I bought another controller. I'm having problems linking it to the drone. I went to DJI forums and posted. I was then met with a message from DJI saying (in not exact wording) that maybe I should buy a more advanced drone. So.... it looks like DJI is really phasing out the Phantom. I thought they were before, and then came the RTK.
But anyway, I still need some help linking.

 

[Starz]

What model number is on the back of the controller?
And, are you certain you have a P4?

 

[Blufx]

Thanks for the reply.
Yep, I'm sure it's a P4 standard. The model number is GL300C.

 

[Starz]

It’s been a while since I’ve had a P4 and controller in my hands. I seem to remember there may be a setting in the app that allows you to switch aircraft from P4, P4Pro, Advanced. May be something visible on YouTube.
I’m not near any of the Phantoms I have at this time or I would check myself.

 

[Blufx]

Hi Starz, when the app opens I have to select the aircraft. I'm wondering if it could be firmware mismatch or something like that. Should I downgrade both and try again?
Thanks again.