Doesn't seem to be working for me, even run as admin & with the most current versions of both Musicbee & the plugin.
For some reason it did let me copy over 2 files, then failed with "object reference not set to an instance of an object". That was drag and drop.
When trying to sync through sync settings, it just aborts the sync no matter what I do.
I tried every different selection in the settings. Same result.
Just got this error, too:
MusicBee v3.1.6345.38589 (Win6.1), 5 Jun 2017 12:49:
System.NullReferenceException: Object reference not set to an instance of an object.
at MusicBee.Media.Storage.#=q5fs6fKGbCbPVIcXzmBHgcdgPORYbSRW1P5FVGK10fTqJrJVT6gGmqX4Yd9SszOyJ(#=qYCOlrFQ5d9XNKhepbbIIpaFQxY6tOq2L0agf_Gr_zHs= #=qP9diMp46GkwqbjFCG7EpJw==, #=qsucckV1WERnrrP$BQTZe88kc5fzVTl8B5jdbSCs5M6M= #=q9TXDktxtLVKZZW2gg5WgpQ==, String #=qR4nBg5zgTXveOdFyV8JZ6w==, Int32 #=qSXL5U2D5_DOSUbIOOJ1f1A==)
at MusicBee.Media.Storage.#=qO8LTIvn8sxiIlyYrKiaWEw==(#=qYCOlrFQ5d9XNKhepbbIIpaFQxY6tOq2L0agf_Gr_zHs= #=qfrqndb4sEqfIeaidxU7SUw==, Int32 #=qGxBlZfThFJ_NoJjAeXT86qVyBz8lvX2pgrYyuaSmG5Q=)
at #=q156AcxeJqRZfdwEcnxPXDQAK9CVra7xeAaqUivLVtcg=.#=q1JfSI6qYjrVpl$ZE7ZWIvw==(Boolean #=qM1QHccsiqtA6Rm4dkWXObg==, Boolean #=qHC2PizOYeDTcKwSgmWsi6Q==, Dictionary`2 #=qfJ2uQqRN6O$zm0pKO$RTgwLLAvjpF25hEmrvuuvpAAM=, List`1 #=qy6uRFFEyhg1fIR2NKNl8_wpReHjP2MmKHo1ZF1mACz0=, Object #=q8w97IrUTuAD4v$$bBwrbWR3Yc8F1h1chOQQy6Kv_Vnw=)
at #=q156AcxeJqRZfdwEcnxPXDQAK9CVra7xeAaqUivLVtcg=.#=qshik6hyIhLlqES_jHcqbrA==(IList`1 #=qBW4QfImybZ8ZLWl04doc3Q==, Object #=qVwYL$lrjc_TMrZs6Fqk5aQdRKJb7EitiYdwOC1bAcrI=)
at #=q_DkWgVwMw6cfu8QKnVn5vAnW2tlzd$qGQzinCN9X5gY=.#=qI$XEEiFG7AlkAbXI8opAw1iSBYRnIZgnL$MKmm9WsXk=(Object #=qJiJ79fhkxZpJR2p4eeTxyg==)
So I got the same error and wanted to figure out what's going on. After an evening of learning to debug dlls I came across an error in
syncedFiles.Add(syncedTrackFilename, 0);
string reencodedFileName = Plugin.MbApiInterface.Sync_FileStart(filename)