Hi guys,
Been watching this thread for a while and would like to make a few clarifying points.
Yes it has happened now and then. The most famous incident is Robinhood in 2020.
@Skylimit and @ex3y7s are correct in that the terms of service are usually very carefully drafted such that any exemption clause would render it very unlikely that any affected user would have recourse under contract or tort (except for very few exceptions, such as if you can prove fraud, or death or physical injury was caused - which doesn't seem to be applicable here). By all means consult your lawyer, but imho it is unlikely you'll be successful in suing them directly.
However, having said that, because Tradier is a member of FINRA/SIPC they are subject to regulation, and FINRA will indeed impose penalties for serious outages (as they did for Robinhood in 2021). Be prepared that the wheels of justice turn slowly, and any such restitution is likely to take years to come into your hands.
If you are an affected user and you wish to take things forward with this, please file a tip with FINRA. If you act fast and can provide lots of detail, you may also (at their discretion) be eligible for whistleblower incentives, which may include a percentage of any penalty imposed.