Apple Watch Pairing

Every time I try to set up / Pair my Apple Watch it tells me to update, I try to update it and it simply tells me that it is unable to be done and quits the set up.

in the photo it says LTE because I tried it both using my internet and not because my internet is very slow, I made sure my Bluetooth was on. I have restarted both my phone and my watch multiple times, I have redownloaded the watch app and even reset my phone itself. The watch has been on the charger and I have tried it multiple times, with and without the charger and I have left it alone on the charger to see if that would make a difference before trying again. Please help me, I bought it second hand and both myself and the seller have been trying to figure out the issue