"The IRA is a single member LLC"

"When entering K-1 on 1040 and checking the box IRA I get an error."

Let's restate this so it makes a bit more sense:

The IRA is your taxpayer's personal retirement account or could be held by a trust that was a beneficiary. The provisions for that type of account's activity are similar to having a trust. There is the ability to hold investments inside of that account. The IRA, then, is invested in one or more activities and holdings, one of which apparently is an LLC formed by the taxpayer, which then has invested as a partner in a different entity that issued that K-1 (not sure why tp created their own LLC to be the interim partner).

Even if all of the IRA is invested in that one LLC, which in turn is invested as a partner in only one entity, all the LLC did is provide a titling and funding mechanism. The IRA is not an LLC. It's an account.