Thank you for your post.
I am unable to replicate the issue. When using FileMaker Go 13.0v5 under iOS 8, I can tap a Container field, and I have the options Camera, Audio, Signature, Photos, Music, and Files.
If you create a new database file with a Container field, are you then able to insert a Signature? This will help me determine if it is a file issue or a FileMaker Go issue.
Thank you for your quick resonse. I am ashamed to tell you that I was working with FileMaker Go v12.0.8. I just downloaded FMGO v13.0.5 and things are running smoothly as expected. Please excuse me for the fuzz!