My Model is no longer able to use the locking feature in Modelit

[nakulshah]

Hi,
Right, so i've built my model (At the beginning I added and locked onto windows no problem), and realised that a smaller window is missing (through my fault). I added the window in, but now im not able to snap onto the window (like how it would show a yellow circle around the corner). I have made sure my locks were all selected, restarted the app and the laptop. but even though all the lock settings are ticked on, i'm still not able to snap onto corners, construction lines ect.... HELP !!!!!