Unable to add script editor webpart on subsite

[LZShann]

Hi,

We encountered this issue when we attempted to add the script editor web part into one newly created subsite.

But it shows this error in the modern view:
Couldn't add this app. Check your network connection and try again

It also showing another error message in the classic view:
Sorry, something went wrong
A different version of this App is already installed with the same version number. You need to delete the app from the site and the site recycle bin to install this version.

For the SPFx app, it was not newly created and is still actively used in the current sites/subsites.

Plus, we also tried another workaround which is to remove the same application in recycle bin and second stage recycle bin. Unfortunately, we're unable to find any similar apps deleted in the recycle bins.

Is there any suggestion or workaround to resolve this? Please let me know if need more information from my end to further troubleshoot on this issue. Your assistance is much appreciated.