Yes, the led lights indeed do go off after 5 seconds, together with the NIC activity led right beside the network port on the AP.
When pressing the reset button, the AP's status led is blinking green for about 5 seconds.
After the AP's reboot , after the reset, the AP status led turns back on again rainbow colored. Followed by sequences of orange led blinking. .
I made sure the AP isn't able to connect to Meraki cloud in two ways.
By removing uplink on the Meraki PoE-switch with the AP connected to the switch, and power the AP with power injector and no LAN connected , as AjitKumar suggested in his post.
In fact , when the AP can connect to Meraki cloud, it is indeed continuing the AP's configuration with SSID's and all.
Which I seek to prevent.