The TSP.gov site states:
I suspect that the new site or vendor interprets "into the G Fund" differently than three years ago. I also speculate that if market conditions at the close of business change the percentages of your funds such that your IFT would increase any fund except G, your transaction will be deemed invalid - and canceled.Each calendar month, you can use your first two reallocations or fund transfers to redistribute money in your account among any of the TSP funds. After the first two of either transaction type, you can only move money into the G Fund.
TSP.gov called me about my IFT failure Monday, September 20th and left a voice message - and others in the following days. I did not listen to any until yesterday because I have found that calls from toll free numbers tend to be scams or solicitations. When I called back yesterday afternoon, the person (not the caseworker who left the previous messages) told me that I could make an IFT now because it was a new month. Not much of a consolation. I'm expecting a return call today from the person working my case. In the meantime, I am debating whether to make an IFT today.