I am using ChIPseeker, however when I open the annotation source file such as Mus_GRCm38_94.gtf, it tells me that is unavailable. However, I was able to see the content of the file. I also have a link such as ftp://ftp.ebi.ac.uk/pub/databases/gencode/Gencode_mouse/release_M18/gencode.vM18.annotation.gtf.gz. I used to able to open and use it and now ChIPseeker tells me it is unavailable. I am wondering what could be the problem.