You didnt mention your Roku model # and firmware version: Settings/System/About
The forums and support articles are your resource - "Agent-Assisted" support is model-restricted (you have to have a higher end model/Roku TV to be eligible):
https://support.roku.com/article/208757038
If you have a model 3920 I suggest warranty replacement (if eligible) or replacement:
https://support.roku.com/article/208757058
https://my.roku.com/upgrade/
Otherwise, start with the requested information and some information your network (ISP, modem/router/gateway brand/model, etc)