Unfortunately, PB.Net has been EOL'ed and there is no direct replacement. As Roland well pointed out, PB 2017 is based on the PB 12.6 "Classic" IDE edition not the PB.Net IDE. Thus, PB 2017 will only work with classic workspaces & targets from previous PB based classic App's. You can see the official response on the Appeon website in the PB 2017 FAQ section and the question "What IDE will I be using to develop apps? about PB.Net.
That being said, the only migration path that could save some or most of your PowerScript code in PB.Net (depending on the features you used), would be to manually transpose the reusable components and code into PB 2017 (ie Copy/Paste). Unfortunately, this could be a vary laborious process.
Regards ... Chris