I installed, using pip, openvino 2021.4.0 and openvino-dev 2021.4.0 (pip install openvino==2021.4.0). My corresponding tensorflow version is 2.5.0. In order to obtain the openvino blob file I used the luxonis on line tool selecting the openvino version 2021.4 and model source: openvino model. The optimizing of a custom tensorflow model goes as follows:
!mo --saved_model_dir ./folder containing the tensorflow model\
--mean_values [127.5,127.5,127.5] \
--scale_values [127.5,127.5,127.5]\
--output_dir ./folder containig the bin and xml optimizer output files
I hope this is of any help