Why isn't there hot water in the shower, when there is hot water in the rest of the condo?
Sounds like there is something wrong with the plumbing in the shower wall or more than likely the shower valve or stem system.  If you are renting this isn't your responsibility.  Not sure of your state's laws but if there is an issue like this in most states you can give the owner 2 notices and a reasonable amount of time and they have to pay for your plumber.  

Again if you are renting I would not fix this yourself no matter your confidence level.  Because mitigating damages will be on you.  

Put something in writing to the owner.  Tell them it is the second form of contact.  Give them a date a few days out and say if it isn't fixed by that date you will hire a plumber to fix it.