You can try https://support.roku.com/contactus , but to be honest your best hope of getting help is to give all the details here. There are several people, users like you, here that are more than happy to help.
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I have the same problem, Roku says has wired connection and internet, but apps like Utube, won't open... that blue circle just keeps going around in circles... Every once in awhile I get an error 16. Nice to see a new router doesn't solve the problem, that was where I was at, buying a new router... couple $100's, plus hours setting up and resetting all of my pc's, ipads, phones, tv, ac, cameras..... I've recycled everything a dozen times, including the Roku (including holding the off button for 30 sec's....), replaced cables. Doesn't work wired or wireless. Any suggestions would be appreciated. Thanks. Larry