I get this:
[01:20:34] CL Platform vendor: Intel(R) Corporation
[01:20:34] CL Platform name: Intel(R) OpenCL
[01:20:34] CL Platform version: OpenCL 2.0
[01:20:34] Error -1: Getting Device IDs (num)
[01:20:34] clDevicesNum returned error, no GPUs usable
[01:20:34] 0 GPU devices max detected
This happening using both sgminer-5.5.5-gm-nicehash & sgminer-5.6.1-gm-nicehash. All other miners (Claymores, Excavator, etc) are working fine on this rig.
Driver: Latest AMD Blockchain driver
GPU: RX580 8GB
OS: Win 10
For some reason, the sgminer initializes only the integrated Intel graphics. Try to boot from your RX580 (as an image output device) and start the sgminer again.
Im start sgminer on RX480:
PS D:\Mining\sgminer-gm-5-5-5-windows\sgminer-gm-5-5-5-windows> .\sgminer.exe -n
[20:49:33] CL Platform vendor: Advanced Micro Devices, Inc.
[20:49:33] CL Platform name: AMD Accelerated Parallel Processing
[20:49:33] CL Platform version: OpenCL 2.0 AMD-APP (2442.9)
[20:49:33] Platform devices: 2
[20:49:33] 0 Ellesmere
[20:49:33] 1 Pitcairn
[20:49:33] Number of ADL devices: 2
[20:49:33] ATI ADL Overdrive5 API found.
[20:49:33] ATI ADL Overdrive6 API found.
That's right, turn it off in BIOS settings and try again to start the sgminer.
Perhaps in the OS itself, there was a conflict between resource usage of the videocard by the miners. At me such happens when all over again I extract ETH, and then I switch on ZEC. It is necessary to simply reboot the OS.