Switchyomega: can not install the plgin.

[dingonet1]

can not install the plgin.
my os is windows 7 with sp1 x64.and download firefox 60.6.1esr (64-bit).when I try to install the plugin from addons in firefox ,it shows network error.

and when I try to download xpi file from github. When install it shows the file is corrupted.

I had tried for english version and chinese version with the same result.

[dingonet1]

I found this is firefox caused.I had to set firefox config item: xpinstall.signatures.required to false.Then it appears good.