connecting wireless issue

so im having a nightmare connecting wireless.
i had 0 problems in december but i tried the end of last month to connect and it wouldnt let me.
was givine me the 8001000A error code. so i contacted sony and they said to reset the system to defaults and so i did and during initial setup was able to pick my router and enter my password and all that. did the tests and it said it was connected.
went to connect to psn and it wouldnt let me giving me that error code.
so sony said to contact my isp about opening ports to enable to connect. i did that still nothing.... so i decided to connect my iphone to the ps3 via personal hotspot and everything worked fine i was able to log in and all that..
so i said forget this went to my isp and got a new modem last night. Arris TG862 hooked it up lastnight. was able to log into psn and all that than i tried to go on the web and it signed me out of psn and than gave me the error code. so i reset the settings again. but this time i plugged in eithernet to the router to connect and it works flawless.
sure it works but still want to figure out why i cant just use it wireless incase i wanted to bring the ps3 in a different room of my apartment.

if anyone is able to help me figure this out that"ll be great!