One of the requirements is that the employer make the same contribution as a percentage of compensation for all eligible employees, including partners in a partnership. This means that the SEP plan must be established under the partnership. The partnership must make the contributions and pass the deductions through to partners using code R in box 13 of the Schedule K-1.
Because the deadline for the partnership to make a SEP contribution for 2021 was the due date of the partnership's tax return, March 15, 2022, it's too late for the partnership to make SEP contributions for 2021.
There is nothing wrong which having opened the SEP-IRA, you just can't make a SEP contribution to it yourself. The partnership can make its SEP contribution to this account for 2022 and beyond should the partnership choose to make SEP contributions.
