Relay default low can't booting the nodemcu

[PeteKnight]

GPIO15 (D8) has to be LOW on power-up, otherwise the the NodeMCU won’t boit.
I’m guessing that changing the jumper on your relay is pilling GPIO15 HIGH at boot.

ESP8266 GPIO pins info, restrictions and features

hi blynkers! the esp8266 mcu is widely used in iot projects. however, most gpio pins on this mcu have special / multiple functionality and are not safe to use in all circumstances. these “features” are still not well documented and not explained in a friendly manner for newbies. i see lots of cases when the “issues” are simply caused by not knowing which pins to use in which case. [esp8266 pin features] here is a basic table for startup. i’ve collected the info from various sources on the i…

Pete.