Does it say “D-” on the adapter? That’s the signal name for USB Data minus (D+, D-, VUSB, GND are the USB lines). Do you have a link to the adapter?
When you just do a simple sketch like
#include <Arduino.h>
void setup() { Serial.begin(9600); }
void loop() { Serial.println("Test"); delay(500); }
do you see any output on PB0? Can you probe other pins of the ATTiny to find the right one (even though it should really be the right one)?