slr no power
There are a couple interlocks which can keep it from powering on... like the battery door interlock and well as the SD card door. Make sure they are closed.
Also... if the camera is "off" it will still blink the SD card activity light when the SD card door is closed. This can distinguish between no power vs the power button not working.
Other than that... is there any history we should know of? Other issues? Damage?
Try removing the lens and power it up.