AppEngine warning - OpenBLAS WARNING - could not d

I try to deploy application on the GC AppEngine. There are no errors during deploy process but application doesn't work (Just show loading page). The only one strange raw in logs

OpenBLAS WARNING - could not determine the L2 cache size on this system

By the way - it works well on my local machine.
This is python web app based on Dash framework

My app.yaml:

runtime: python37
service: service-name
instance_class: F2

entrypoint: gunicorn -b :$PORT main:app.server

Requirements.txt:

Flask==1.0.2
dash==0.34.0
dash-html-components==0.13.4
dash-core-components==0.41.0
dash-table==3.1.11
gunicorn==19.9.0
google-cloud-pubsub==0.37.2
requests==2.21.0
pandas==0.23.4

I just had your same problem with pandas and Dash and found your question (hoping it would give me some light). After being stuck for several hours, I found the answer, and came back to share :-)

If the only error that you're seeing is the OpenBLAS warning, most likely the app is working well. After debugging this problem for several hours, I found that as Dash and Pandas consume a lot of memory, the F2 instance is not able to handle the web app properly and fails due to lack of RAM memory. Please try changing in your YAML/JSON configuration file your instance to the highest possible automatic unit with more RAM memory, and then it will probably work:

instance_class: F4_HIGHMEM

EDIT: Google App Engine now supports more instance types. Check the docs of instance types: standard instances

In addition, please keep in mind that the first time you run this web app, it will take considerably more time to execute. If you check the logs you'll have several prompts like the one below. Just wait a little bit more

This request caused a new process to be started for your application, and thus caused your application code to be loaded for the first time. This request may thus take longer and use more CPU than a typical request for your application.