Gateway problem

Hi,

I have installed on-premise gateway in server and connect it to Power BI report 3 months ago. Schedulling for refresh data from oracle DataBase was working well for a month. From 2 months ago, however, the schedulling is not able to work and the gateway is not connected. The error message is showing that our data gateway is offline or couldn't be reached Even though the On-premise gate way is perfectly being turned in Server. For 2 months, I have been monitoring the probem this and turing on manually the gateway in server.

ps. As soon as I connect with between On-premise gateway in server and Power BI report to use data on Schedule, It shows Successful connect. After 3 hours, or even 2 hours, the connection is died.

Please, Let me know the solution.