My federal returns was accepted on February 12, 2021. However, where's my refund at the IRS has not marked the returns as "approved". Anyone experiencing the same issue?

After the tax return has been Accepted by the IRS (meaning only that they received the return) it will be in the Processing mode until the tax refund has been Approved and then an Issue Date will be available on the IRS website.
See this IRS website for federal tax refund FAQ's - https://www.irs.gov/refunds/tax-season-refund-frequently-asked-questions