I am trying to design a simple power supply using TNY268 , I connected the circuit as in the attached schematic

Where the input of the attached schematic is connected to the output of a bridge and smoothing capacitor , I understood from the datasheet that at the beginning of each cycle the EN/UV pin is sampled to see if its pulled down , then the next cycle is disabled other wise its enabled , I Ignored the feed back optocoupler and left the pin floating (not pulled down) so that the duty cycle is always maximum , switching is not happening except when i connect the HV source then the switching stops

so why is switching stops , what I am missing or misunderstanding from the datasheet ? Is it necessary to use optocoupler ? Can I fix the duty cycle to always maximum and always switching on for testing/Educational purpose at the beginning ?

Thanks