Don't power/fire it up again. When facing the front of the amp the two small pins of the 300B should be on the left side of the socket assuming the amps/sockets are stock (check to see if this is how they were installed). You already know that the 6922 goes to the left (the 5687 to the right).
If the 300B's (one or both) were installed differently Audion's US rep/importer has been through this before and can advise you on what to do from there. Chances are the amp will require service.
Don't have the address handy, but a web search of "OSS Services Audion" should take you to the rep's site.
On a side note if you have JJ 300B's their pins are too small to make proper contact in the Audion's sockets (@ least the pins on my JJ's 3 years ago were). The sockets can be adjusted/shimmed to work, but all in all JJ's were a poor match with the amp (my least favrite 300B by a long shot in the SN).