If the gun does not react at all after pulling the trigger with an attached battery, first check if the battery is charged and functional.
Additionally, check the wiring to see if any wire connection has been severed.

You may hear slight movement or noise from the motor, or feel the battery and grip getting hot when pulling the trigger.
Do not keep pulling the trigger, this might result in the MOSFET unit or the motor starting to smoke.

Please take a look at the video below, as this issue could be caused by the motor sitting too high and binding up:

Full-Auto only issue:

If you are running into issues with the pistol only firing fully automatic in either semi or full-auto, this is usually caused by the trigger bar being bent too far up or down. The following video explains how to resolve this issue:

Semi-Auto only issue:

If the pistol is only firing semi-automatic, the trigger bar needs to be bent downwards, instead of up, as shown in the video.

Burst on semi issue:

If your SSE18 is firing in bursts of two to five shots on semi-automatic, this is caused by the trigger contacts being too narrow. This can be resolved by widening the contacts marked in the picture below.
To do so, take off the cover plate to gain access to the trigger contacts, you can then use tweezers or a similar thin tool to bend them away from each other.

Ensure that no battery is connected to the gun while doing so.

If the SSE18 is misfiring and not feeding the BBs properly, this is often caused by the usage of poor quality BBs. We recommend using trusted high-quality brands with the SSE18, as these are known to work well with the gun.

Another thing that can cause feeding issues is a too high or low hopup setting. The hopup can be adjusted with the wheel underneath the slide, please try different settings to check if the feeding improves.

If the issue only occurs on the standard 29-rd magazines, the problem may be with the width of the cutout. If the paint layer at the top is too thick, it can cause the BBs to sit too low, which results in them not being able to be picked up by the nozzle. This can be remedied by slightly filing or sanding down the area of the feeding lips marked in the picture below.

If you are experiencing power issues, always first check if you are using the correct BBs and hopup settings. Please check if the chronograph you are using for measuring the power is set up correctly and has the appropriate BB weight set.

This usually only happens when the hopup is not adjusted properly. To do so, you can take off the slide and turn the hopup wheel to adjust it.

If you are still finding the gun to not be hopping properly, please first thoroughly clean the inner barrel, or check if any parts of the hopup assembly are damaged or missing.

If the SSE18 is only firing slowly, the battery is most likely discharged. Ensure to use a fully charged battery for the best performance.

This could also be an issue with Gen1 SSE18s, which still have the Gen1 MOSFETs installed. These are not as efficient, we recommend upgrading to the Gen2 MOSFET:
https://novritsch.com/product/sse18-mosfet-harness-gen-2/ 

On older versions of the SSE18 magazines, the BBs may spill out due to the pressure from the feeding lips being insufficient.

You can follow this video which explains how to improve BB retention:

If the magazine release button has come off, fallen out of the pistol or got stuck, please follow the video below to reinstall it.

If you have lost it, or it has broken, you can find a new magazine release button here:
https://novritsch.com/product/sse18-magazine-release/