This video shows how to check your certificate (cer file) downloaded from OPDA to see its capabilities and the IMEIs inside it. OPDA had problems issuing certificates around June 22nd, and some people are complaining that they are getting the error "constrained by certificate" when installing apps signed with OPDA certificate. With devcertlist.exe you can see if your IMEI is included in the certificate you downloaded from OPDA. If it is, you can sign you apps without having to worry. If it is not, you have to find a way to request another certificate (have to ask in OPDA if they can issue a new cert for you with the same IMEI, because the cert you received does not contain your IMEI).