AVG's email signature does not work!

I cannot change my setting on the email signature. It was not enabled by default. I have just installed it yesterday. I want to place the AVG email signature right after my email. But that doesn't work.
I opened the settings and ticked the box 'add a signature to the end of sent emails' for many times. However, every time when I close the settings and open it again, the 'tick' in the box disappear. I have tried many times, I think it is 23 times. However, that doesn't work. 
Can anyone help?

Hi Alan,

We are sorry to hear this.

We will help you to sort out the issue.

Please share us the screenshot of the settings to investigate further.

Let us know the version of the program.