I had to delete Lightroom 6 due to ISP troubleshooting, how do I get it back? It is gone from my computer.
Download it from the Adobe website and install it. When run for the first time Sign in using the Adobe ID you used to buy it and enter the serial number you got for it.
Never ever uninstall programs, especially programs from Adobe, to trouble shoot ISP issues. Those issues are either ISP network related or Router/Modem related and very very very rarely a computer issue.
But if you were having internet access issues on more than one device, 2 or more computers or a computer + Phones and or Pads, then it had nothing to do with any device connected to your home or work LAN.