Looks like you have set "isDomainIsolated": true, in the package-solution.
Modify it to "isDomainIsolated": false, and then do the process to package the solution again by doing the gulp tasks and then re-upload the app to the site collection app catalog.
Usually, domain isolated webparts are used for communicating securely with resources outside of SharePoint and rendered inside iframe. Also, these can sometimes request permissions which require tenant admin's permissions, so they can't be installed in site collection app catalog.