Digital Signature is not popping up/ not accessible

I'll just make everything clear, recently i have downloaded a DIN Application PDF form which can filled in by enabling & accepting some security settings, and it connects with the external server i.e. Ministry of Home Affairs (INDIA), here is the image ▼

After filling all the data, finally in the signature region, when it says sign here with your digital signature, when i click the box my signature is not popping up although i've created my digital signature before and added it to Trusted Root Certification Authorities but still i can't access my Digital signature, here is the image ▼

I saw so many videos in Youtube..when they click the signature box like the above, then their Digital signature pops up then type the password and it's done! but iam not getting any Digital Signature

Please, anyone help me in this...Thanks in advance.