@Akul Good day,

If Range extender does not detect 5Ghz wifi from Nokia Router , you could try suggestion here: 

• Put Range extender close to router during set up
• Change a different 5GHz wireless channel on the main router:

If the main router’s 5GHz channel is set to Auto or between 149-165, it is recommended to  change it to a channel between 36-48.

If still the prolem, may i know do you have EU/ US verion range extender? 

@Akul Good day, 

Sorry for the delayed reply. 

Tp-link RE (EU) version support does not support Band4 channel  (149-165) on 5Ghz to comply with CE certifications. 

It is recommended to check of router's Wi-Fi channel is on 149-165. (you may download a wifi analyzer software to check router's channel)

If unfortunately Router is using a channel between 149-165,  you could try multiple reboots on the main router and see router will switch to a different channel. 

It is also recommended to contact Nokia / Airtel L2 support, and see if they could help change channel, some ISPs are able to change channel remotely.