Can you say something about what server platform you are running?
In broad general terms a lot of the trouble in upgrading to Seafile 8 has been the Python dependencies. Examples are here, here and here. In Ubuntu, for example:
sudo apt -y install python3 python3-pip python3-pil python3-ldap python3-urllib3 libpython3.8 python3-setuptools python3-mysqldb python3-memcache python3-requests ffmpeg
sudo apt install python3-django-captcha
sudo pip3 install --timeout=3600 Pillow pylibmc captcha jinja2 sqlalchemy psd-tools django-pylibmc django-simple-captcha python3-ldap