SIM800L Blinking issue , does not perform stable

Hi Team,
I have recently purchased SIM800L Module and it malfunctions. Power supply given is 4.2V 2A

Indications
1.modules were working good for 1hour then continuous blinking (tried with different sim cards also
2. modules blinks for 6to8 times stops and again blinks
3. modules doesn’t blink it self
these are tested on 6 different modules with different Sim card

​kindly help me in understanding what is the issue and how can you rectify this ​

What is blink rate when you say continous blinking? every second or faster?
If using battery, it can be discharged after 1 hour. If data, then data can be exhausted after an hour. Please check.

This can happen if power source is unable to supply enough current for connecting to network on boot up. Ensure a stable 2A current capable source.

Can be multiple reasons. Power, PWRKEY pin etc. Check voltages and see if you making PWRKEY low.

Hello Bro…
This is the same happening with me GSM module Blink everyone second …
It works perfect for about 1,2 time then it start blinking and not connecting to any network can u tell me what is the problem… Please i need help… i have bought 3 GSM module sim800l but same problem with every module please help me