Check that your US Lacrosse membership does not expire prior to the start or end of the spring season. If it does, you will need to renew it - https://login.uslacrosse.org/login/login
When entering the US Lacrosse membership number, make sure to type of the numbers in and do not copy/paste from the US Lacrosse website. If that still does not work, remove the 00’s that are in the front of the number and try again.