CiviCRM URL issue: CiviCRM theme is not loading after CiviCRM update to 5.26.1 version
can you add below lines in your civicrm.settings.php?
global $civicrm_paths;
$civicrm_paths['civicrm.root']['url'] = CIVICRM_UF_BASEURL . '/sites/all/modules/civicrm';