If your Office 365 version of Skype for Business has not updated to the most current version, you can manually force it to update.
Also hitting the end of the road are Office 2007 and Outlook 2007.
Once the updates are downloaded, it no longer has to be connected to the network to install the downloaded updates.
Once the compressed update files are downloaded, they will be uncompressed and moved from your Download folder to the Apply folder.
The longer it's been from your last update, the larger the update download will be.
If the download process is interrupted for any reason (such as power outage, network disconnect, etc), it will continue downloading the update rather than restarting from the beginning.
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Microsoft on Tuesday officially ended support for all of these services, meaning that you won't be receiving any updates or security patches from the company moving forward.