This is usually a driver issue. Reinstall the Mediatek USB VCOM drivers and try a different USB port/cable.
For devices powered by the MediaTek MT6877 (Dimensity 900) chipset, the standard software used for flashing is the SP Flash Tool mt6877 flash tool
Known for "Exclusive" support for MT6877 on Vivo devices, enabling features like Safe Format (resetting without losing photos/videos). This is usually a driver issue
, stripping the device of its ability to connect to cellular networks. Conclusion the ecosystem includes commercial alternatives:
While SP Flash Tool is the standard, the ecosystem includes commercial alternatives: