If you are using Windows, here’s a generic driver/ adb/ fastboot repair …
- Disconnect the phone from the computer.
- In Control Panel - Programs and Features:
Uninstall everything with “MTP” or “ADB” in its name. - Reboot Windows.
- In Control Panel - Device Manager:
Enable View - Show hidden devices, and then uninstall every possible ADB, MTP and smartphone device, hidden or not. - Reboot Windows.
- Connect the phone again
Windows should then install working MTP drivers again automatically.
If this doesn’t work, the problem is probably on the phone’s side (*).
If you had adb and/or fastboot before, they might have gotten uninstalled now if they originated from a formerly installed package like “Minimal ADB and Fastboot” or something similar, so (and it’s better to use the following anyway) …
- Download the current Android SDK Platform Tools.
- Unzip the ZIP file to e.g. C:\platform-tools (you can unzip it to wherever you like).
-
Add this path to the Windows “PATH” environment variable, so adb and fastboot could be run from everywhere again without always having to prefix them with e.g.
C:\platform-tools\.
(*) At least if MTP access to the phone worked before. Just as a reference … If there would have been a problem with MTP from the start, it could have been due to a Windows N version. (“N” = without Media Player, result of an old antitrust case)
A Windows N version would need the “Media Feature Pack” before it can do MTP. This should be installable via Settings - Apps - Apps & Features - Optional features (or something like that, German locale here) in current Windows 10 N, for older Windows N versions there were dedicated downloads … https://support.microsoft.com/en-us/help/3145500/media-feature-pack-list-for-windows-n-editions