Hi @Marc Oo ,
Great to know that and thanks for sharing the update here.
By the way, since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others.". and according to the scenario introduced here: Answering your own questions on Microsoft Q&A, I would make a brief summary of this thread:
[SharePoint Server 2019 - App Installation - Stucked on Install status]
Issue Symptom:
Hello, I'm trying to put into place a modern search webpart in a preprod SPServer2019 environment. We've found a .sppkg that does the job and installed it on the dev env. The app works. When it came to preprod env, we had to create an appcatalog (with its app management service and subscription settings services application). We've uploaded the package into the catalog and it's been deployed properly. Then, we went to add the app to the site where we want it to run, and that's when the issue occurs : the app stays greyed-out in the site contents forever :
and it's stucked on install status (shown with get-spappinstance -web 'http://mysite'):
I've checked that the services (Sharepoint Timer and Administration) on both farm servers are running, i've configured the app urls and followed MS Learn procedure step by step. That's the third day I'm getting stucked on it, and it starts to get on the nerves of the people i have to explain why nothing happens, so i kinda need help and I can't find that much information on the net, plus i'm totally new to sharepoint server.
Current status:
I've allready checked permissions and services, aswell as investigating ULS. I've noticed a timerJob named App Installation Service that is responsible to install/uninstall apps on SharePoint. So, I had to make this job running and it solved the issue.
You could click the "Accept Answer" button for this summary to close this thread, and this can make it easier for other community member's to see the useful information when reading this thread. Thanks for your understanding!