Left Click in trackpad and mouse sometimes not work!

Hello there, arqdiegot.

It sounds like you're seeing unexpected behavior from your Magic Trackpad. The following Knowledge Base article offers up some great pointers for resolving potential issues:

Trackpad or Magic Trackpad is jumpy or erratic - Apple Support

Follow these steps and recommendations to resolve the issue.

• Be sure only one part of your finger is touching the trackpad and that you are not resting your wrist on or very close to the pad. The trackpad may interpret this as your finger touching it and make the cursor move in that direction.
• If you're using the Magic Trackpad, be sure the batteries are fully charged.
• Moisture collecting on the trackpad can also cause this issue. Wiping off the trackpad with a cloth or tissue usually fixes this. If the issue goes away when a piece of paper is put between the finger and trackpad you may want to consider purchasing a Teflon applique to fit over the pad to prevent the moisture from having direct contact with the trackpad. Before installing the Teflon applique, confirm the trackpad is clean and dry. You can use a mild glass cleaner sprayed onto the cloth (not onto the trackpad itself) to clean the trackpad. Note that oil or lotion can also cause the same issue.
• Jewelry may also cause interference. Try removing rings or bracelets and see whether the jumpy or erratic behavior disappears.
• Apple has had some reports of this behavior on Mac notebooks being used with power supplies made by a third-party company. If you are using one of these power adapters, unplug it and try running from the Apple battery to see how the trackpad behaves correctly. Also, try using the Apple AC adapter instead of the third-party AC adapter. If the trackpad behaves normally while running from the battery, there is most likely an issue with your adapter or outlet.
• If none of the above resolve the issue, try to rule-out software not created by Apple as a cause. To do so, start in Safe Mode.
• Magic Trackpad can act erratically when there is interference. See Wi-Fi and Bluetooth: Potential sources of wireless interference for more information.

Thanks for reaching out to Apple Support Communities.

Kind Regards.