Problems with WordPress multisite directories/url structures and admin access after migration

I’m trying to migrate a multisite WP installation to a new server. The network consists of a simple parent site that redirects users to one of four subsites based on their location. E.g. if a user from the UK visits the site, they’re redirected to the site.com/uk subsite.

Before the migration, each subsite’s theme & plugin resources (images, css, js etc.) were available from the subsite’s url, e.g. site.com/uk/wp-content/themes/uk-theme/images/image.svg. After migrating the site to the new server, the resources are no longer available from the subsite domains, but are available from the parent site’s domain, e.g. site.com/wp-content/themes/uk-theme/images/image.svg. This is causing all the stylesheets, images & js for each subsite to 404.

The other issue is that, although the main multisite network admin is accessible (site.com/wp-admin/), the subsite’s admin panels aren’t accessible, and going to site.com/uk/wp-admin, for example, produces an ERR_TOO_MANY_REDIRECTS error.

I feel like the two issues might be linked somehow but I’m not sure. Does anyone know why this might be happening and how I might be able to fix it?