The TLAST gets generated correctly if you use the Vitis Vision libraries. I have tested with both Vitis_HLS and Vivado_HLS.
XFopencv 2019.1 has bugs that have not been fixed. I opened an issue last year that still has not been addressed. it looks abandoned now on Git.
The issue you are reporting looks the same as in this thread.
The issue I am reporting is simple. The Vitis Vision core pass simulation and COSIM but stall on hardware. I have tested both AXI and streaming modes and both fail.