I have gone through the whole Basic workflow and gotten to Lightroom to exporting the pictures. The prosess starts to export the 4826 pictures, and all is good for 2-3 hours. When I then get back I see that the pictures are no longer previewed in lightroom and a messages tells me; There were no rejected photos to delete.

Further down the page is says that 0 of the 4826 Pictures are selected. What is going on? I was fine for over 2 hours then this suddenly happended

This is strange, since at no point LRTimelapse trigger the "delete rejected photos" tool.
To resume the export, check the LRT_ folder and see until which image the export succeeded.
Now go to Lightroom, select from the following imagenumber to the end, then open the export dialog and in the LRTExport Dialog under "Advanced Settings" set "Initiali Sequence Number" to the number of the first of the selected images.

For example, if you find that the last exported image is LRT_1234.jpg, select all images from 1235 to the end in Lightroom and enter 1235 as "Initial Sequence Number".