does a loss of power mean acatilic converter
Maybe yes or maybe no. You could have the codes read and post them here . The actual codes.
It might. If the engine is burning some oil between changes it may have plugged the catalytic converter enough to cause the failure to pass emission tests first then if it gets worse it can cause enough backpressure on the exhaust to cause loss of power on the engine. Have it tested for back pressure.
Could be a couple dozen things. we need more information, like actual symptoms, whatwas it doing up to just prior to the power loss, maintenance history. The more info you can provide, the better the suggestions you will receive.