It looks like you are using the walk around mode of the route tool. That icon means it cannot go where you want it to go because it will cause it to violate the DRC requirements. It'll likely be a clearance or keep out rule being violated. Switch it into manual mode (the icon next to the walk around icon (currently selected) in the top toolbar when the route tool is active) and you should see live DRC violations appear as you route to the pin. Open up the DRC window and see what the actual errors are and this will tell you what the problem is.
Best Regards,
Rachael