"Because he is the only owner of the business, I use form 1040 and Schedule C to report his business"

Because he is Not running the business under a Corporate entity (C or S)? That's a different reason than what you stated.

The forgivable loans are not supposed to be reported on 1099-Misc. Even when they are forgiven, they are not supposed to be reported on a 1099-Misc. For instance, the SBA made 6 loan payments, the principal is not reportable, the interest still is deductible, and the Banks were told this.

Loans are not reported on taxes; they are debt to be repaid and not income.

A City grant to a business is supposed to be reported on 1099-G, and it is taxable for Fed, except for specific grants such as Shuttered venues and emergency response.

https://www.irs.gov/newsroom/cares-act-coronavirus-relief-fund-frequently-asked-questions

https://www.lmc.org/resources/cares-act-funds-form-1099g/

"All these aid are due to the pandemic and correspond to the 2020 taxes "

But for What? Rent, Expenses, Wages? An Air Quality Improvement grant?

Everything matters.

I doubt anyone on the internet can help. You will need to get the taxpayer to contact the grantor, perhaps.