RPI 3A+ V11C is not booting

After several tryouts to get the V1 Telraam working on my RPI 3A+ i am looking for support. I flahsed the V11C on my SD Card and the RPI is not booting. The green ligth is always blinking. I tried different flash tools (RPI flashing tool , Baleabatcher, Win 32 , etc) but its not working. I also tried to flash an RPI OS fpr the 3A+ and this is booting, so it looks like there is no problem with the sd card or the RPI. Could it be that the boot partition is not working corectly?

sorry it took so long to respond - -
as you said - it is probably the card - most of the times the card is the cause
you need a type 10 or higher
how much GB? at least 16 - i use alway 32GB
for a fresh install always use a new card
good luck