If you have a license for PrestaBay 1.5.x, you can upgrade to PrestaBay 1.7.x version. Information about version located there http://prestabay.involic.com/prestabay-startup-version-upgrade-1-6-0/ and https://prestabay.involic.com/prestabay-startup-update-1-7-0/

First of all please go to page http://involic.com/purchase/prestabay-integration-startup-upgrade-to-16 to go purchase upgrade. 

Instruction for update located there http://prestabay.involic.com/HowToUpgrade

1) Before doing upgrade please backup sources of the current version. FTP path /modules/prestabay
2) Before doing upgrade backup DB. PrestaBay tables started from ps_prestabay
3) After upgrading open page Catalog->Ebay->Config and click on a link "Get License."
4) Please open page Catalog->Ebay->Accounts and re-assign all ebay accounts 
5) Please open page Catalog->Ebay->Marketplaces and check that you have all using marketplace details.