Not able to fill Checkbox or check radio

I am using it like this:
`pdfFillForm.write('pdfFiles/new_pan.pdf', { "Shri": true }, { "save": "pdf", 'cores': 8, 'scale': 0.2, 'antialias': true })`

It just makes the checkbox field non-clickable in the generated pdf.
For radio, I have tried giving the caption value as explained in the readme file... Same this is happening t radio fields as well