Migrating from MX7 to CF10 - CFX trouble

I've taken a .jar file that contains classes used with the HSBC CPI gateway - does things like hash encoding of data.

It seemed to work well with cfmx7, but I had a bit of trouble getting it recognised by cf10.

However, it is now recognised. I had to do the following:

1) Put cpitools.jar into <WEB-INF>/lib

2) Tag Name: cfx_HSBCHashGenerator, Class Name: com.clearcommerce.CpiTools.security.HashGenerator

3) Restart CF (not 100% sure this is necessary)

4) Call a script with  <CFX_HSBCHashGenerator SharedSecret="#ss#" HashElement="#datainput#">

However, I get this error message:

Now, I know that the .jar file was just fine in MX7. Is this a change for CF10, or is there something else going on?

Thanks for any help - I'm tearing out the little hair I have over this one!