Softbricked HTC One M8, Fastboot command doesn't recognize phone on fastboot mode

(Kind of a noob too) I have a RUU file i downloaded from HTC webite (websiteRUU_M8_UL_M60_SENSE70_MR_BrightstarUS_WWE_ 6.12.1540.4.zip) but the problem is that I have no OS on my phone, fastboot doesn't recognize my phone, it only does when i go to TWRP recovery but it doesnt in regular recovery mode. HELP!!! :(

(I have an unlocked bootloader, S-On, and TWRP installed)

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