What version single bay/single drive My Cloud unit do you have? The older first generation v3.x/v4.x firmware My Cloud or the newer second generation v2.x version My Cloud? The process to unbrick them may not be the same. And the firmware file needed for each version is different which means you generally cannot use the first gen firmware to unbrick a second gen My Cloud and vise versa.
Some have had luck with Fox_exe’s unbrick methods.
To unbrick properly you MUST know what version, first gen or second gen, of single bay My Cloud you have otherwise the unbrick process will fail if you select the wrong image (img) file.
Generally one can find the firmware version number which indicates generation version by accessing their single bay/single drive My Cloud Dashboard. v3.x or v4.x is first generation, v2.x is second generation. Otherwise, look at the bottom of the My Cloud for the “P/N” number. Generally if the P/N number ends with “-00” then its a first generation My Cloud. If the P/N number ends with “-10” then it is a second generation My Cloud.