The Oppo A37 runs on a MediaTek (MT6750) processor, not a Qualcomm Snapdragon. On MediaTek devices, "Fastboot mode" is limited .
A: Fastboot mode is a waiting state. It is waiting for a command from a connected computer. If you are not connected to a PC, nothing will happen. If you want to leave, follow the "Exit" instructions above. how to open fastboot mode on oppo a37 better
Note: On some regional variants of the A37, the combination might be Volume Down + Power The Oppo A37 runs on a MediaTek (MT6750)