Azure DevOps| Cache#2 - CACHE_RESTORED always evaluating to false - azure-devops

Question

Why is CACHE_RESTORED always evaluating to false?
My solution has two projects. For both projects, I added property RestorePackagesWithLockFile set to true, I build the solution, then added the packages.lock.json files to source control. I've made a series of changes to where the caches should have been generated by now, however pipeline runs always say There is a cache miss.
Here are the relevant steps for the pipeline:
steps:
- task: NuGetToolInstaller#1
- task: Cache#2
inputs:
key: 'nuget | "$(Agent.OS)" | **/packages.lock.json,!**/bin/**,!**/obj/**'
restoreKeys: |
nuget | "$(Agent.OS)"
nuget
path: $(Pipeline.Workspace)/.nuget/packages
cacheHitVar: CACHE_RESTORED
- task: NuGetCommand#2
displayName: NuGet restore
condition: ne(variables.CACHE_RESTORED, true)
inputs:
command: restore
restoreSolution: ${{ parameters.solution }}
feedsToUse: select
vstsFeed: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx...
Here is the output of the pipeline run:
Starting: Cache
==============================================================================
Task : Cache
Description : Cache files between runs
Version : 2.198.0
Author : Microsoft Corporation
Help : https://aka.ms/pipeline-caching-docs
==============================================================================
Resolving key:
- nuget [string]
- "Windows_NT" [string]
- **/packages.lock.json,!**/bin/**,!**/obj/** [file pattern; matches: 2]
- s\Project1\packages.lock.json --> 9999999999999999999999999999999999999999999999999999999999999999
- s\Project2\packages.lock.json --> 8888888888888888888888888888888888888888888888888888888888888888
Resolved to: nuget|"Windows_NT"|123456781234567812345678TxQePOdHp6IqQWh9w6w=
Resolving restore key:
- nuget [string]
- "Windows_NT" [string]
Resolved to: nuget|"Windows_NT"|**
Resolving restore key:
- nuget [string]
Resolved to: nuget|**
Using default max parallelism.
Max dedup parallelism: 192
ApplicationInsightsTelemetrySender will correlate events with X-TFS-Session xxxxxxx-xxxx-xxxx-xxxx-xxxxxxxx
Getting a pipeline cache artifact with one of the following fingerprints:
Fingerprint: `nuget|"Windows_NT"|123456781234567812345678TxQePOdHp6IqQWh9w6w=`
Fingerprint: `nuget|"Windows_NT"|**`
Fingerprint: `nuget|**`
There is a cache miss.
ApplicationInsightsTelemetrySender correlated 1 events with X-TFS-Session xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxx
Finishing: Cache
The fingerprint value 123456781234567812345678TxQePOdHp6IqQWh9w6w= (masked) is the same value in the previous two pipeline runs.
What am I missing?
Update:
the path $(Pipeline.Workspace)/.nuget/packages - this doesn't exist on a hosted agent. Need to find the right path?