Photoshop trouble with photo and layers

-photoshop version : 24.5

- Platform : windows 10

Hello all,

Recently I am facing one issue while working with Photoshop. After importing file to photoshop and applyping few adjusments and editing, I merged all layers. then edit on that layer. but after sometime, thumbnail of merged layer became transparant. adjustment layers are visible but merged file not. and effects also turned off. why this is happening. all the work i did go in vain.