Doc says dig sig allowed, but won't let me dig sign

[#1]

Hi, I have a fillable PDF that I need to digitally sign, and it won't let me do so. I've checked the extensions and it says that I should be able to digitallyl sign the document. I've filled in the various text areas that I need to fill, but when I get to the area where I need to digitally sign and I open the certificates tool, the options are greyed out and I literally cannot even select digital signature to either insert it in the fillable area OR draw a box for the dig sig to go in. There are no error messages; it just doesn't even give me the option. What's the deal?

[#2]

Is there a signature field in the PDF file?

[#3]

No, all the fields where signaturs need to go are fillable text same as the rest of the form. But the security settings for the form explicity say that digital signatures accepted.

[#4]

Have you created the form?