Failed to decrypt using provider 'RsaProtectedConfigurationProvider'. Error message from the provider: Bad Data

Hello,

I have been given a web.config file from a 3rd party that had the connectionstring section encrypted.  The 3rd party instucted us to decrypt the file using:

C:\Windows\Microsoft.NET\Framework\v2.0.50727>aspnet_regiis -pdf "connectionStri
ngs" C:\Decrypt

then we made some changes to the connection string and encrypted the file again using:

C:\Windows\Microsoft.NET\Framework\v2.0.50727>aspnet_regiis -pef "connectionStri
ngs" C:\Decrypt

this has worked, however when trying decrypt the same file which we copied to a 2nd web server we get the following message when trying to decrypt the file:

Failed to decrypt using provider 'RsaProtectedConfigurationProvider'.

I did a google search and most answers were to export the RSA key container to the 2nd web server, but trying to do that on the 1st webserver gives this error: The RSA key was not found

please advise

thanks