External table is not in the expected format error ?

Dear All

I am working on vb.net application and I have a code which does a certain job and it is working but sometimes it gives me this error with some excel files and it is working with other files, and sometimes it works once without error and next time it gives this error
This line of code gives me this error

it gives me this error
EXTERNAL TABLE IS NOT IN THE EXPECTED FORMAT

I installed Access Database Engine and it did not solve the problem

Thanks, Regards

Moheb Labib