From tsp.gov:

ThriftLine Issues

We are working to resolve a technical issue at one of our call centers that may delay your ability to speak to a ThriftLine Participant Service Representative. If you experience an issue, please call back at a later time. You can also visit the My Account section of tsp.gov to perform interfund transfers, contribution allocations, and other transactions. While you’re there, you can ask a TSP representative a question by clicking on “Message Center” on the left.