Steps to reproduce the behavior

Prereq. Logged in as Author or Contributor user.

1. Create a new post.
2. Add a block on page.
3. Click on Toolbar > Hamburger Menu > Add to Reusable Blocks.
4. Click on Add Block on top left of the masterbar.
5. Click on Reusable tab.
6. Scroll down to bottom and click on Manage all reusable blocks.

What I expected to happen

User is able to view and manage reusable blocks they have created.

What actually happened

User is unable to view any reusable blocks, even ones they have created.

Context

User scenario #manual-testing.

Browser / OS version

Browser: Safari Version 14.0.2 (16610.3.7.1.9)
Browser: Firefox Nightly 87.0a1
OS: macOS Big Sur 11.1 (20C69)

Is this specific to the applied theme? Which one?

N/A

Does this happen on simple or atomic sites or both?

Tested on Simple. Untested on Atomic.

Is there any console output or error text?

No

Level of impact (Does it block purchases? Does it affect more than just one site?)

Minor - user must request someone with higher access (eg. Administrator) to modify the blocks for them.

Screenshot / Video: If applicable, add screenshots to help explain your problem.

https://user-images.githubusercontent.com/6549265/106679358-52cfec00-6571-11eb-8525-0ad66d6fe8e6.mov