There are a couple problems with your project that I had to fix before I could even simulate. I suggest starting from the small building blocks without and transmission link and test their operation. Often projects get very complicated and there are many parameters that could be set wrong.
The first thing I saw was the the bit generators were set incorrectly. The units were in Gbit/s and the stated value was 56e09, which is already in Gbit/s so the resultant bit rate was much larger than you probably wanted. Furthermore, the symbol rate should be set to half of the bit rate since you are using a qpsk format.
Try changing these options and troubleshooting the project without the transmission link.
Cheers!
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