Recently, Roku has updated its software, and the developer mode can't be acceptable for some Roku models.
We highly suggest using another device such as Andriod, Firestick or Apple TV, PC or Laptop.
Note: You can reset your Roku device to factory default settings. Then try to install the app again. Sometimes this will solve the issue.
To install the app, please follow the instructions on the below tutorial link:
https://crm.alliptv.tv/index.php?rp=/knowledgebase/5/How-to-setup-Roku-TV-or-Roku-Stick-Device.html
