Importing Invoices returns "Error: Sheet name is not valid. Please, check the sample file."

Hi,

I am trying to import invoices from a XLS, I downloaded the sample given by Akaunting and after I upload the XLS I get the error "Error: Sheet name is not valid. Please, check the sample file.

No idea how to debug it, I want to say also that I am running Akaunting on my server.

Thanks

I didn't realize that each sheet has a particular name I changed and it works fine.