sometimes the plugin are not showing in admin panel plugin list. i have to download all the plugin again from github and remove the plugins in my project in order for them to work again. what will be the problem ?

Do you use the source code version or the compiled one? It looks like compiled plugins dissapear from Plugins folder in the Grand.Web project (or main store directory).

i used the source code version to replace them with the official project ones. the older plugins were with the project when i donwload it..