AGAIN Roku app cannot find IP address of Roku Express

UPDATE TO ORIGINAL POST: I thought I had found a solution to this problem by turning off the privacy settings on my iPhone WiFi settings. This stopped working pretty quickly. Then the app started working randomly again for a few days, without having to change any iOS settings! Unfortunately, the situation has now reverted to not being able to connect. I have confirmed that the app works with Roku’s at other houses. My internet provider says the issue is not theirs. Does Roku have a solution yet? 

My roommates and I have been using the Roku app as a remote for our Roku Express specifically because of the ability to play audio through headphones and not disturb each other. It was working for months, but in the past few weeks the app would randomly drop the connection then have to reconnect. Today, the app could not connect to the device at all. I have restarted the app and the device, checked the WiFi setting, and even factory reset the device. The phone and the device are linked to the same WiFi, the IP addresses are both 192.168.1.XX. No VPNs are involved. The connection on the Roku device says it is excellent. When I try to connect manually with the IP address, the app says there is no device found there. I am inputting the correct address, as I am copying it directly from the “About” section from my TV screen. Control by mobile apps on the device is set to default. The WiFi is Spectrum. We only have one network available, and we cannot even access the Access Point settings. The phones have local network access enabled for the app. We have tried with multiple phones, all iPhones running the latest iOS, so we believe it is a problem with our device or the app, not the phones. We have gone through every step given by Roku’s troubleshooting guide, and nothing has changed.