Hi, Not sure of the IP issue as not seen that but have seen plenty of people getting the problem of installing Instagram in Bluestacks error with the APK file, had it myself. Decided to revisit the problem and found th solution.
First Open Bluestacks, Next I Googled OI Filemanager and downloaded the APK file for that, clicking on the file installed it in Bluestack which notified me that untrusted apk files were blocked so i changed that setting to allow. OI File manager installed on Bluestacks, open the App in Bluestacks and you get a load of folders to browse, i'm running on windows and the Instagram file was in my download folder so i browsed to the Windows folder in the OI Filemanager app (not the downloads folder in the app as that is different) and from there you get to My Documents and from there to the windows download folder, selected the Instagram app APK and it installed fine with no errors like invalid file error i was getting before.
Once you have done all that i could run the app and the screen window would resize to a mobile device type window and log into Instagram using the login i created from my Mobile device when i setup the app on that. If you are still getting IP issue then perhaps you ISP or country is banned, if you have it running on a laptop try connecting over wireless like at a cafe or somewhere so your not using your home ISP IP.