Try a 10k pullup on reset combined with 470nF between reset and GND. This creates a soft start that allows the smps to stabilize before the attiny tries to start. In all likelihood it tries to start but drops into a brownout detection state because the smps hasn't ramped up reliably yet.
Thanks for your reply. Is it ok to implement an RC circuit on the mainboard which contains all 144 MCUs for a soft start?
I mean without a pull-up resistor on the reset pin. Because it will cause a huge amount of men power to solder all 10 k pull-ups and caps.... I build separate chips that contain MCUs and a mainboard to supply data and power...
I think that would work, yes. But you'll have to analyze any possible interactions between the 144 reset pins; e.g. together they will draw a little current that may be significant enough to influence the component choice in the RC circuit.