Be sure to read https://yatse.tv/wiki/debug-yatse-kodi-remote to provide necessary logs and information.
I have been using Yatse on my Fire tablet connecting to OSMC for a long time with no problem. I recently purchased a FIre Stick, and after installing the remote app for the Stick, Yatse will no longer connect to OSMC. Yatse sees OSMC on the network, and if I try to reconnect from scratch using the wizard it says that it is unable. I have tried changing the port for Kodi, and I have tried uninstalling the Fire Stick remote.
2019-02-25 22:24:44.754 Verbose/KodiLogger: <--  HTTP FAILED: java.net.SocketTimeoutException: failed to connect to /192.168.1.16 (port 8080) after 5000ms
2019-02-25 22:24:45.123 Verbose/KodiTCPListener: [email protected]: Stopping TCPListener
2019-02-25 22:24:49.199 Verbose/KodiServerLocator: [email protected]: Cleaning host detection resources