Tinsipit

Hello, I'm trying to set up my laptop so that I can play the Tekkit Classic modpack on a long train-ride I'll be going on soon. I won't have any Wi-Fi (nor a hotspot) for the duration of the trip, so I'm trying to make sure the offline mode is functioning However, I'm running into some problems when I disconnect from the Wi-Fi (Keep in mind that I have legitimately purchased Minecraft under a Mojang account and used it to log into the technic launcher with the "Remember me" checked; everything works perfectly normal when online). When opening the launcher, I'm greeted with the log-in screen that allows me to select the account I have used previously, I select it and click login, and am greeted with a prompt saying "The auth servers at Minecraft.net are inaccessible. Would you like to play offline?". I select "Yes", but the prompt simply closes and nothing occurs, even after a minute waiting. This occurs every time I try to open the launcher even after restarting. Fortunately, running the Technic launcher as an admin will skip the login menu and take me right to the launcher around half of the time. I navigate to the Tekkit Classic option and click "Play Offline", and the launcher quickly disappears and reopens in the exact same window with Tekkit Classic still selected. This occurs each time I hit the "Play Offline" button. If anyone could share some insight on this problem, that would be amazing. I appreciate all the work that went into this launcher and would love to kill sometime with it on the travel.