Cannot change / remove Router's Bit

Are you using a suitable wrench to remove?
Ensure you are using the correct wrench or tool provided by RYOBI for changing bits. Using the wrong tool can make it more difficult to loosen the collet nut.

Is the collet nut overtightened?
The collet nut might be overtightened, making it difficult to loosen. Use the appropriate wrench (included with the router or 17mm or 19mm size) to turn the collet nut counterclockwise to loosen it. Turn it in the opposite of the bit's rotation.

Is the bit stuck in the collet?
Over time, bits can become stuck in the collet due to tool dust, debris, or rust. Ensure that the trimmer is unplugged, or the battery is removed for safety, and then use a penetrating oil or lubricant on the collet and bit to help loosen it. Allow the lubricant to penetrate for some time before attempting to remove the bit.

Collet nut not engaged
The collet nut needs to be engaged to hold the spindle in place while changing the bit. Locate the collet lock button or mechanism on your trimmer and ensure it is properly engaged before attempting to loosen the collet nut.

Is their dust and debris in the collet or around the bit?
Check the collet and bit for any foreign objects or debris that may be obstructing their proper function. Remove any obstructions carefully.