Note from Leslie - this was published by @Emon_423837 and should be attributed to them NOT to me. My apologies for getting something irrevocably wrong on the backend with the attribution. Everything after this sentence is Emon's work, not mine.
Initial setup of BIG-IQ CM or BIG-IQ DCD
Unable to login into the BIG-IQ GUI but able to login using SSH
This type of problem happens when your local machine and BIG-IQ have much time difference.
Step for solution:
Step_1&2: Configure NTP Server on BIG-IQ & Set timezone