Not creating Customer invoice number correctly

We did an audit of our customer invoice folder to make sure we have saved a hard copy of all invoices raised.   We found that between December 2021 - April 2022 - 37 invoice numbers had not been created.    We have MYOB auto create the invoice numbers so dont know why these invoice numbers are not being created.   We haven't had this issue previously.  Numbers not used 7006361, 7006367, 7006370, 7006374, 7006377, 7006394, 7006401, 7006429, 7006437, 7006457, 7006458, 7006494, 7006507, 7006508, 7006512, 7006520, 7006528, 7006532, 7006541, 7006542, 7006549, 7006550, 7006551, 7006553, 7006554, 700658, 7006559, 7006563, 7006565, 7006566, 7006569, 7006573, 7006591, 7006600, 7006608, 7006609, 7006621.   Wondering why this is happening ?