Brother, don't panic. If you can show proper explanation through LOE, IRCC will allocate you enough time to submit FBI PCC. My suggestion is, raise a CSE with an LOE (Letter of Explanation) having a topic i.e. missing FBI PCC on subject line. Include proof with CSE if you already have applied for FBI PCC, otherwise just ask for time first and then raise another CSE with the proof later.
A lot of people submitted FBI PCC later after e-APR submission, it's normal, but what you are missing is the LOE to IRCC during e-APR.
Act quick cause I fear you don't have enough time left.
Thanks