Dear Aspirant,

When you move to section only registered candidate sign in and fill my application form and password it shows invalid application no and password you tried it many times it shows same again and again then you should try at registering candidates only. Sometimes the technical glitches create problem. So try again after some time. If the problem still continues try to login with another device or browser. If then also continues try to contacting to the concerned authority about the problem and write an e-mail to NEET with you application no. for further clarification on your problem.

Hope this helps.

Good Luck!