To fix SPA112 connection issue follow the instruction:

First, reconfigure the port, by assigning the VoIP VLAN, CDP wasn’t working correctly at our situation.

[edit interfaces ge-2/0/41 unit 0 family ethernet-switching vlan]
-      members Users;
+      members Voice;

Second, disable the automatic firmware upgrade from the IPFX, for this go to web UI and login as admin.

Then, navigate to voice → Provisioning → Set “Upgrade enable” as no