If you need to restart your FiveM to join the server (Different game version or pure mode):
Fivem needs to restart
Right-click on the FiveM launcher
Press Open file location
Make a new shortcut from the Fivem.exe and drag it to your desktop
Right click the new shortcut and select Properties
Press Shortcut and locate the Target box At the END of the target box, put a space then type -pure_X -bYYYY
Find the server build and what pure mode it runs on. (This should say in the restart message when you try to join the server)
Replace the X with the pure mode the you found earlier (ex. 1, 2, 3) and YYYY with the server build. (ex. 3095, 2699, 2944) Example: C:\Users\lmarket\AppData\Local\FiveM\FiveM.exe -pure_1 -b2699