Does not see an external hard drive 2.5 usb 2.0

Can I fix it?

Fix what? More information is needed. Are you trying to connect the external hard drive to a single bay My Cloud device? If so is the external drive properly formatted in a supported format for the My Cloud?

I connect to the usb port, the disk is formatted in NTFS. How correctly to format? My Cloud EX2 Ulta

Because you are using an EX2 Ultra you may want to see the dedicated subforum for the EX2 series to see if there is any specific discussions related to your issue. This subforum is generally for a different device, the single bay My Cloud device.

The link provided above shows the recognized formats supported by the My Cloud line. In certain cases if one has more than one partition on the hard drive it may cause the My Cloud not to properly mount the correct data partition.

One can use their favorite internet search engine to find out how to properly partition and format a USB hard drive on their computer’s operating system.