1: You need to set "ModeOverride" to either FullAuto, SemiAuto or Burst.
2: It depends. If your gun has "AllowAllAttachments True" then it's the attachment fault, if it allows only specified attachments then it means that you need to change the shortname of the attachment to correct one. Example: Gun has "AllowAttachments swsilencer" then shortname of your attachment should also be "swsilencer". If everything with it is fine then check the attachment settings, especially the "AttachmentType" line.