From the TSLAC website:
The Request for Public Assistance (RPA) deadline is now 5:00 pm, Oct. 31, 2017. This is a critical deadline and supersedes any previous deadlines provided by the State. If your arts organization, cultural institution, or government entity misses it, you miss the opportunity to be considered for, and possibly receive, federal disaster assistance. Please do not pre-judge your organization about its eligibility. It’s most important that you file that RPA now. If, for some reason, your organization turns out not to be eligible, it will at least help FEMA know who and where you are so we can determine if other resources can be brought to bear to help you.
The FEMA News Release about the October 31 RPA deadline can be found at https://www.fema.gov/news-release/2017/10/07/deadline-governmental-jurisdictions-and-private-nonprofits-request-0.