Hi,
Most probably because the filter needs to be changed.
Here’s a [https://products.geappliances.com/appliance/gea-support-search-content?contentId=23974|link] that may help
Here’s a link to the [https://products.geappliances.com/MarketingObjectRetrieval/Dispatcher?RequestType=PDF&Name=49-40342.pdf|user manual] for the microwave oven taken from this [https://www.geapplianceparts.com/store/parts/assembly/JVM1650BB007|webpage]. Scroll to p.40 for information regarding the filter