Hi, what version of NMM are you using? If you read the news on the Nexus site you will se that the Nexusteam has done some server changes, so you will have to get the latest update to NMM which is NMM (0.46.0) found on the top of the mainpage in the middle (the link) and you need to download and install it manually i think, since older versions of NMM doesnt work at the moment.