For my project, I am intending to build a cocktail cabinet. Therefore, there will be one main power switch that will power up everything at once, monitor, Pi and speakers. During my simulations of this with everything just plugged into a power strip, when I turn the power on, I get no display on the monitor. If I power up the monitor first and then the Pi all is fine.

It took me awhile, but I finally figured out the issue and the solution.

Apparently, the monitor will pass information to the Pi regarding resolution and frequency, from which the Pi configures itself to support at boot up. If however, the Pi boots before the monitor turns on, the display won't work.

There are 2 ways to solve this, both in the config.txt

One was is to hard code the monitor specs into the config.txt. To do this you need to line in the code

hdmi_group=X
hdmi_mode=X

Where X is a value you enter that corresponds to the specifics of your monitor. This works OK, but I've found it to be a bit quirky and if you change monitors you'll have to recode.

The Second and what I thing better way is to simply delay the boot just long enough to let the monitor start. In the config.txt file you add this line to the code

boot_delay=X

In this case, X equals the number of seconds you want the delay. I used 3 seconds and it works fine. I may be able to get away with less (I didn't experiment), but a 3 second delay is hardly noticeable.