After upgrade to PBA 6.0 the online store redirect links are loaded much longer than in PBA 5.5.x.
An additional call GetCustomersListByVendor_API is made, which takes relative much time on installations with big number of accounts. The call is not necessary here, a bug with id PBA-62340 was submitted about the issue.
To workaround an issue until the bug is fixed, comment the line below in
//$accounts = $stp->GetCustomersListByVendor_API($stp->GetVendorOrResellerID($VendorID));