Cannot boot - grey blank screen & keyboard does not work
Since two days I am trying to boot my Macbook Air 2012 from USB and I cannot pass the blank grey screen in the beginning. There is no Apple logo just a grey screen. I tried to use various key combinations (recovery mode etc.) but no keyboard input does work. It simply nothing happens and I stick to the grey screen forever. I also did a SMC reset with the battery disconnected.
For some time I tried to find solutions for my "grey screen of death" problem but nothing worked. I should also mention that my Macbook is victim of the Toshiba SSD problem and my SSD does not work anymore properly. I am using the PNY StorEDGE SD Card Storage and I boot from this storage.
Thank you for your help already! Hopefully you can give me some advice.