Sometimes, Jio does Firmware Update on the FTTH Router resulting in WiFi connections not working. What the update does is changes the SSID and hence the problem.
How to Change SSID of Jio FTTH Wifi Router ?
On your mobile, turn on "Mobile Data Internet".
From your MyJio App, Access the Settings and Change the SSID as well as Password.
Since, your FTTH is ied to the App, any changes in the MyJio App will get reflected to Jio Servers in Mumbai which in almost real time pushes to the FTTH Device (Router).
Now after 5 Minutes, when you turn on "WiFi" on your Laptop / Mobile, you should be able to see the new SSID. Choose to connect, enter the Password and you are all up and running.
Update the new Password in your WiFi Printer as well.