I’m a real beginner so I’m just trying some simple recipes to ease myself into cheesemaking.  My first attempt at 30 min mozarella (no culture just citric acid and rennet) resulted in edible cheese but it wasn’t stretchy.  Can anyone tell me why?

My second attempt came unstuck right at the beginning.  I added salt and citric acid to the milk and heated it (water bath) but the temperature climbed too high 38C.  I brought the temp back down to 32C but it took about 10mins.  I then added vege rennet (diluted with water) and almost immediately it curdled. After 20 mins there was a lot of liquid and it had not set.  Can anyone explain to me what happened?

Thank you for your help.

Welcome to the forum. This has been discussed in the past.
One reason can be the type of milk used, other is too much acid. Nabil has posted a process that has worked well for him.

Welcome Maggs, try this one, I have success with it:

4 liters of raw cow milk
1.5-2 tsp citric acid diluted in 1/2 cup water
5 drops of vegetable liquid enzyme (strength=1 drop/liter) diluted in 2 Tb water
Salt

Pasteurize milk. Heat to 72 deg C and cook to 28 as fast as possible. I do that in my kitchen sink sometimes adding ice to the water.
Add the diluted citric acid, stir and heat to 28-32 deg C.
Add the enzyme solution and stir thoroughly for 5-10 sec. Turn heat off.
Wait 5 minutes, check for clean break (the coagulum should separate from the sides of your vat). If not, wait a bit more.
Cut the curd in 2 cm cubes.
Transfer the curds to a cloth lined colander applying slight pressure to accelerate draining.
Transfer the cheese to a glass bowl, put it in the microwave on highest grade for 1 minute (the temperature should be about 41 deg C). Using two wooden spoons (or your hands) stretch the cheese dough. You may salt the cheese dough during stretching or put it in brine at the end.
Put the cheese dough back to the micro for another 30 seconds, stretch again.
Repeat until you get a shiny smooth cheese dough.

If you would like a softer Mozz, let the curds drain less and do less stretching.