Make sure that "Ctrl Receive" on your Blofeld's Global menu is set to "on" so that it will receive change messages from Patch Base. Also, make sure that the "Device ID" setting in the Patch Base Blofeld module (under the "Global" tab) matches the Device ID setting your Blofeld itself.
If you're using a USB cable to connect your iPad to the Blofeld, you might have trouble sending patches from Patch Base to the Blofeld. This happens because the Blofeld's USB MIDI port doesn't handle larger amounts of sysex data coming in at once very well.
You can fix this by opening the MIDI settings in Patch Base (tap the MIDI icon in the top left of the editor), and activating "Limit Transmit Speed". You can leave the speed slider set at 3125. Doing this should slow down Patch Base's MIDI sending enough that the Blofeld can handle it correctly.