Hello Veepo,
Any animated GIF I've made in PhD has looped, by default, when played in appropriate software like Win Photos, GIMP, IrfanView etc.
If you're using it in PDR, it will only play once through its set number of frames. To make it repeat, the GIF needs to be inserted repeatedly. PDR can't force it to loop.
Can you give any further information about how you intend to use it?
PIX
PIX YouTube channel