So, long story short I have tried every trick I know. I have turned my modem and router off and on. I have turned my tv and my Roku off and on. I have reset the network connections. I have updated my software. I have updated my apps. I have called my internet provider and it's nothing on their end. My Roku keeps connecting to my wifi, saying "poor download speed" and then disconnecting, no matter what I do. Its been going on for three and half hours now. Please help. I have the Express +.
My experience with front line support people at ISPs is that they seldom are kept up to date on short term internal problems.
Having said that ...
Here's what has worked for me to re-establish my net connection. Before getting a new router recently I had to do this on my most used Roku, a Streaming Stick+, several times a month.
If that doesn't fix it, try disconnecting the power to your Roku for a few seconds. When it comes back up, see if you then can set up the network connection.