You need to open port 9981 and 9982 on your router. Instructions for every router differs so I cannot guide you, you need to do your own research on this. I do not recommend hosting on a laptop as you need to meet certain uptime (98% uptime? not too sure) or you lost your SC as collateral.
Connect the rasberry 3b before the first boot to Network cable and router, and some TV so you can see what happen.!! ....If not ,you perhaps can't get Network to work. I tryed first boot whitoute conection.. and can't find out how to Change IP. I fixed it wite rewriting the Image to the microsdcard and connected everything before first boot and it worked . After that you can see the ip of the siaberry in the prompt in TV , or you use a toll like ""fing" for ios or android to find the ip if you can't find it in your router .It was named " recovery" in my router and not siaberry or rasberry some confusion for me. After that you can hit the ip in every browser you have in your "Lan" configure the siaberry to your conditon. I use the IP cause siaberryos.localblabl did not work for me. It loads the chain more than a day ,wallet unlocking trigger cause of new Wallet Setup need a few hours. But it works.
I've got a similar problem.
End of july, I sent coins from Poloniex to my Sia-UI wallet but never received them. Poloniex gave me a TXID which doesn't exist on the blockchain (sia.explorer).
I created a support ticket but only received automatic answer. No one at Poloniex is really looking into it.
It's now been 6 months since I lost my coins ....nobody cares...
Transaction Date : 2017-07-26 05:50:10
Thank you for your reply. Those are my life savings. I would commit suicide if I lose those coins. Do you know anyone that I can contact with? Say, someone working in Poloniex dev team or something? I am desperate now...