MQ 2400: MQRC_UNSUPPORTED_CIPHER_SUITE
Did you copy the Cipher Suite name from your other application into DevTest? You're using the old MQ step, so the cipher suite field is under Server Connection Info -> Advanced.
Is your other application Java-based? Could there be some other setting or environment change that you had to do there?
There are troubleshooting steps here for your particular issue here, towards the bottom under section 4.6 and 4.6.1: IBM MQ and SSL/TLS
The page is written for the new IBM MQ Native step, which I highly recommend you use if you're starting from scratch. The last resort troubleshooting step, which involves installing the IBM JCE provider, requires the newer IBM MQ Native step.