First, make sure your battery is good and full of water.
Then make sure it is being charged.
Use a multimeter and measure across your battery terminals.
If you read around 14.5VDC then the battery is being charged. If after a while this 14.5-VDC does not go down then your battery is probably bad.
If you read around 13.5VDC then the battery is charged, and your problem is elsewhere.
If you read around 12 to 12,5 VDC then your battery is not being charged. If this is the case, then you need to check that your RV is plugged into 110-VAC and that the Converter is operating.
From your symptoms, I would suspect the battery first.