Missing Length Tag

Hello,

            For a private project I am using c++ for reconstructing packets after transmission. After reconstruction I am adding a tag to the output stream but once it gets to the "Tagged_stream_to_pdu" block it throws the following error 
"Missing a required length tag on port 0 at item #0 thread[thread-per-block[160]: <block tagged_stream_to_pdu(172)>]: Missing length tag"

I have used the tag debugger block however it says there is a tag present so I'm not quite where to go from here after also searching the internet for a solution with little luck as well. Here is the portion of the code where I create and add the tag if anyone can guide me if I am actually adding the tag properly.

tag_t tag;
      tag.offset = this->nitems_written(0);
      tag.key = pmt::string_to_symbol(this->lenTagName);
      tag.value = pmt::from_long(this->frameSize);
      add_item_tag(0, tag);