From the documentation of style-src:
'<hash-algorithm>-<base64-value>' A sha256, sha384 or sha512 hash of
scripts or styles. ... In CSP 2.0 this
applied only to inline scripts. CSP 3.0 allows it in the case of
script-src for external scripts.
So based on this the hashing specification cannot be used for external styles but only for inline ...
It looks like that with Chrome (but not Firefox) you also need to explicitly allow 'unsafe-hashes' since giving the hashes alone seem to apply only for script and style sections and not attributes. See 8.3. Usage of "'unsafe-hashes'". With that your CSP should look like this:
style-src 'self' 'unsafe-hashes' 'sha256-7kYG54iPGE/Vf+GFqobEwpF9bfCAVA/...