New O2 sensor and still getting CEL on

Hi I had a new catalytic covertor installed at meineke and the check engine light came back on had it read  at autozone and the code was p0430  i took it back to meineke and they said it was the bank 2 o2 sensor , they put a new one in and 2 days later the check engine light came back on . Someone said that the computer needs to adjust to the new O2 sensor before it will go off . has anyone ever heard of this  or should i be concerned . My emissions test is at the end of May and i wont  pass with the CEL on . Any help  would be grateful as i really cant afford to put any more money into the car right now . Thank you . Johnnyboy130