Did you claim a dependent in 2019 who is not being claimed by you in 2020? The credit is based on the number of dependents you claim, not their identity. Is your income above the start of the phase-out? $75,000 for single and head of household and $150,000 for married filing jointly.
Is this child awarding you the $2000 child tax credit? Then it must also be eligible for a stimulus payment and there must be some other reason that a further amount is not allowed.
