Dear candidate, some problems faced by people in downloading JEE Main admit card are:

• Slow Internet
  

• Server Issues(Many students try to download at same time so server crashes)
  

• Incorrect Credentials(Check once more details filled by you)
  

• Incomplete Registration(Those who have paid successfully application fees and completed whole process will only be able to download admit card. Some application forms get rejected due to incomplete details)
  
  

However, if you have no such problem then try to contact at JEE Main helpline numbers: 7042399520, 7042399521, 7042399525, 7042399526. Contact at this number between 10am to 5pm.

Hope, it helps!