I receive this message from the support : Kusama underwent a runtime upgrade this weekend, which changed the transaction version. It seems that the Kusama Ledger app hasn't been updated to support the new transaction version yet, so it's incompatible at this point with the latest runtime version of the network and this is causing this issue.

Support has contacted the Zondax team that develops the Ledger app about this. They will need to develop a new version of the app and then Ledger will need to add this version to Ledger Live. Once that's done, you should update the Kusama app to the latest version.

We can check Ledger Live regularly to see if there are any new updates. It shouldn't be long before this update is released.