Why is my computer suddenly saying Could not reconnect to all network drives?

I think I know what that means, but I don't know why it's doing it. I've had my Lenovo laptop for almost 3 years and never saw that message before. Then yesterday, I had to install a new part on my laptop. I took the whole thing apart, and put it back together, and now this message pops up every time I turn on my computer. Everything works fine. So what does it mean, and how can I fix it?

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