Locked up brake pedal

When you say the pedal is locked in the up position normally that means they are very hard to press and you don't have assistance. This means the first thing we need to do is find out if when pressing the brake pedal that the pushrod on the master cylinder is moving. The pedal may be hard to press but if the pushrod is moving then it is not locked up and we just need to figure out the lack of assistance.

If it is not moving then the master cylinder is the issue.

There are a number of ways to find out if the push rod is moving but I think the easiest is to just go through the adjustment procedure that I attached. Or you can just lift the wheels and step on the pedal really hard and see if the front brakes stop the wheel. Clearly make sure they spin first then step on the brakes.

Let me know what you find and we can go from there. Thanks