Tigo optimizers are factory-configured in the "on" position, which means voltage as high as open circuit voltage (Voc) is present at the outputs as long as a PV module is connected*. In most cases, a PV module connected to a failed optimizer will produce power just as it would without an optimizer connected.
*For an MM-2ES Dual Maximizer with two PV modules connected, the output will be the combined voltage of the two modules in series. For Smart Modules with reduced Voc, check your datasheet.