Downloaded below file from bootstrap section of the APIC-EM IWAN app -
ip address dhcp
pnp profile IWAN-PNP-PROFILE
transport http ipv4 xx.xx.xx.xx port 80
copy running bootflash:IWAN_RECOVERY.cfg
The router is running on version 15.5(3)M2 .For some reason, its the router does not start with this configuration. Its just booting normally. Used 4451 as well with 3.16 code version and it worked perfectly. Also, in IWAN documentation, it says the supported version on ISR G2 is 15.5(3)M2a. But there is no such version (may be I am missing something)
Check the name of the configuration file on the USB stick. It should be ciscortr.cfg.