Can someone explain the difference? ?

Question

I’m learning English and I would like to see if someone could please explain the difference between this two sentences? Which one sounds more natural? 

Example: 

I’m not sure as to why they are getting this error, so I’m going to send the email to my supervisor to look into this for us. 

I’m not as to why they are getting this error.  I’m going to send the email to my supervisor to look into this for us. 

Answer 1

Forget "as to" and you don't need "this for us" when "it" will do. You can then write it either way

I’m not sure  why they are getting this error, so I’m going to send the email to my supervisor to look into it.

Or you can split it into two sentences

I’m not sure why they are getting this error. I’m going to send the email to my supervisor to look into it.