HELP! Can't connect with Windows computer

This is tough to help. It may be networking, server change or something in OSX side.
What happens if you Browse for the servers? Finder, select Go : Connect to server (cmd-k) and lower right is button "Browse". Do you see your server? If not, OSX is not seeing the service.

This way you avoid need to know the IP number or even type of protocol. While service on Windows may be Samba, on OSX side it can show as smb:// (samba) or cifs:// (whatever that means). My network - by now - has only Mac servers, so my experience with Windows servers is limited in the last few years.

This may sound funny, but are you sure you are on the same network? Like in my house I have guest network and my own network, from the same wifi point. Samba does not pass through between those networks. In my case the IP number spaces are different, so it is easy to say, but I am not sure if that is always. And since you rest the system, may be computer connected accidentally to the second network?
Check your OSX firewall options in Security & Privacy. Try turning off firewall for testing and see, if that helps.
Is the samba drive setup to require security? Limited to specific IP addresses?
I remember at some point it was needed to allow some lower level for security on one of the systems - and I do not remember which one. Try to check for some up to date on line how to which may mention that. There was something about one system requiring higher level of security protocol or whatever.
There is lots of options and while this should simply work (and usually does), it is difficult to diagnose.

 

can't help witn Windows 7 but to help later - I make the IP's fixed on several of my devices to make it easy to remember.
Like network printers - other computers ect.

there are a few free /low cost net scan software that will list all your devices and Microsoft had the MAP function some where in the network access tab

I just use a low cost one disk NAS to hold shared files to exchange between mac and windows.

The old Apple airport router can even have a Flash drive plugged in to help exchange data

 

No hammer, patience. May be you just identified where the problem is. You can connect with other computer (I assume same Windows version?), then the question is : what is different between the two computers? Is one Win 7 and the other Win 10? Or same version? One Home version and the other Pro? There were networking differences between those versions...
If other OSX computers can connect with that one specific problematic Windows computer, then what is different between the two OSX computers?
This is simple process of elimination. Hammer will make solution impossible to find.