I bought new computer and it will not authorise my sony ereader PRS-350. Error message Error getting licence E ADEPT DOCUMENT TOO SHORT

I bought a new computer and ADE will not recognise my sony PRS-350 ereader.  I get the message: Unable to download, error getting licence, licence server problem, E_ADEPT_DOCUMENT_TOO_SHORT.  I cannot read my purchased books because I cannot download them.  All answers will be greatly appreciated.