I install scratch 2.0 458.0.1. on my mac (High sierra 10.13.2) and installed Scratch Device Manager as instruction
(I also install same scratch 2.0 with my MacBook pro 2017 sierra, same problem as described as following)

When I open my scratch offline, I can see the “Lego wedo 2.0” icon in the extension library.

I can select it and click ok. However, nothing was added in the “more blocks” section

When I open the “Scratch Device manager”, it only showed the animation about how to add an extension.

However, I can add Lego wedo 2.0 blocks on the online scratch 2.0 on this website, I can add wedo 2.0 blocks in scratch and new blocks are available
(scratch 2.0 can't work by MAC safari, only by chrome!)

The scratch device manager showed the “connect” button immediately after I added wedo 2.0 in online scratch 2, and the function works fine

However, after I close the online scratch, the scratch device manager revealed the instruction of how to add extension again.

I think there the problems is related to offline scratch 2.0 for mac?

I can save the project from online scratch 2.0 but the wedo 2.0 blocks became “undefined” if I open it with my offline scratch 2.0.

You might want to post your topic here

Moved to “Connecting to the Physical World.”