The clutchpedal seems to work but does not engage and the fluid level reamains full

Park you car on a level surface. Set the parking brake on you car; start the engine and let it get to full operating temperature; pop the hood and while the engine is running, check the transmission fluid by pulling out the transmission dipstick. Wipe off the dipstick, reinsert it into the dipstick tube all the way down, then pull it out again and check the fluid level.
As you check the fluid level, observe the fluids' color; any discoloration, other than a bright red color, means the transmission is going bad, especially if the fluid smells burnt.
If the fluid passes the visual and smell test, make sure the transmission fluid level is within or between the fill and full marks. If you need to add transmission fluid, make sure you use the right type based on the car manufacturer's specs which are located in your car's owner's manual. In absence of one, call your local dealership or parts store, they can easily look it up free of charge. Of course if the level is low, add a little fluid at a time through the dipstick tube while the car is running- checking the fluid level frequently.
Then check the PCM for any DTCs; are you pulling any fault codes?
If there is damage to the bands, clutches, or solenoids, a tear down and rebuild of the transmission will have to be done; and it is costly

Check transmission fluid level. If low then add to top of full line. If fluid is full already, is it burnt looking or smelling? If answer is yes, replace transmission. Sorry, but not much will keep the transmission from working. If the fluid is really low then the the pump won't have enough to engage the gears. However chances are if the fluid is that low then it is burnt looking and smelling too which means that the transmission will need major repairs.

If your transmission is a 700r4 (4l60) you have a reverse band that engages when you want to go in reverse. since it drives forward your low reverse clutch and your fwd clutch are working. This leaves the band which was probably slipping now is not engaging.

I would check the brake fluid level. It is under the hood on the drivers side up near the windshield. There will be a white/clear reservoir with a black cap(Might mention DOT3 only on it). Open that up and check the fluid level, it should be at least 1/2 full to full. (there is marks on the reservoir that show what full is).

first thing i would try is changing the transmission fluid out and filter, i beleive its almost 8 quarts. use a full quart of lucas transmission additive with the new fluid. if this doesn't help, the transmission will either need replaced or rebuilt

Check master for fluid level, check line going to slave unit, check slave unit (any leaks, you have found problem) If master is full, it may be internally bypassing in that case it may not leak but will not put pressure into the line. (fluid goes around piston instead of being pushed) If master is low and no obvious leak found, look under dash where clutch rod goes into the back of the master. you may find fluid there.

Transmission fluid is low. Drive the car 15 or 20 miles to heat up the transmission. Check the transmission fluid level with the car running in neutral with the parking brake engaged. Add transmission fluid to come to the full mark. Go slow when adding fluid. DO NOT OVER FILL!! This should fix your problem.

Check the fluid level. Low fluid levels will not allow the transmission to engage. If fluid level is full, more than likely you will have an internal problem.

If the fluid is full , it sounds like the trans pump is loosing prime. If it is there will be a code set. The code will not always turn on the light. Go have the codes checked. If it does have a loss of prime code in the trans computor and the fluid is full then you will need the trans pump replaced

Check fluid level in the clutch master cylinder. It is probably low. If so, top it off and bleed the clutch system then check for lkeaks.