Instructions on installing Java 16:
To play Minecraft 1.17+ it is required that you have Java 16 installed. Follow these instructions to install it
1. Download Java 16 from here (Windows x64 msi): https://adoptium.net/releases.html?variant=openjdk16
2. Run the installer and make sure to change "Set Java_Home variable" and "JavaSoft (Oracle) registry keys" to "Entire feature will be installed on local hard drive" during the installation
3. In the Technic Launcher Options in the Java Settings section set your Java version to "OpenJDK 16 64-Bit" if it is not there you will have to click on "Find Another Version" and navigate to C:\Program Files\Eclipse Foundation\jdk-188.8.131.52-hotspot\bin and select the javaw.exe file
4. In the Java Settings section of the Launcher Options un-check the box that says "Use Mojang Java runtimes"
5. Add more Memory in the Technic Launcher Options (between 4 GB to 8 GB is good)
6. Install the pack, hit play, and enjoy!