If they are not answering emails it might be an idea to check that they are still operational?
http://www.ebr.org/ has official records for all the companies in a lot a of european countries. For some countries you can also get previous years financial statements, contact persons and current board members.
A personal visit is unlikely to accomplish much. The best way would probably be to hire a german debt collector. (Inkassofirm, schuldeneintreiber - something like that). Be sure to send them proper documentation, and you might want to do it quickly - many european countries have time limits for keeping claims valid.
These debt collectors usually add their costs handsomely on top of your original claim so you will likely pay little or nothing if they are successfull - the german company will have to cover the cost of getting them to pay. (You might want to check out what happens if they don't succeed though). Usually the debt collectors will get the money but it can take time.
However if the german company has valid reasons (or just something they can use as an excuse) for claming that your claim is invalid you might be in for a long and costly run. To counter that you will ideally have some documentation that the order was well received or that they got what they wanted. More likely though you might be able to document that they didn't complain about anything within reasonable time.
We ourselves usually pay small international orders through credit card, and large orders using Letter of Credit. Not foolproof by any means, and LOC is costly, but a lot better than nothing.
international business issue
Linear Mode
