GitVersion not incrementing versions for NuGet setup

I'm struggling to get a GitVersion config working for the way we want a NuGet repo to work. Changes need to be committed to feature/* branches, and then merged back onto main. Unfortunately, none of the +semver: xxx comments on our commits are doing anything. We tried using the new Mainline config, but that doesn't seem to work either. Can anyone spot what's wrong with this config please?

Our GitVersion.yml file:

mode: ContinuousDelivery
next-version: 1.0.0
branches:
  {}
ignore:
  sha: []
merge-message-formats: {}

/showConfig:

assembly-versioning-scheme: MajorMinorPatch
assembly-file-versioning-scheme: MajorMinorPatch
mode: ContinuousDelivery
tag-prefix: '[vV]'
continuous-delivery-fallback-tag: ci
next-version: 1.0.0
major-version-bump-message: '\+semver:\s?(breaking|major)'
minor-version-bump-message: '\+semver:\s?(feature|minor)'
patch-version-bump-message: '\+semver:\s?(fix|patch)'
no-bump-message: '\+semver:\s?(none|skip)'
legacy-semver-padding: 4
build-metadata-padding: 4
commits-since-version-source-padding: 4
tag-pre-release-weight: 60000
commit-message-incrementing: Enabled
branches:
  develop:
    mode: ContinuousDeployment
    tag: alpha
    increment: Minor
    prevent-increment-of-merged-branch-version: false
    track-merge-target: true
    regex: ^dev(elop)?(ment)?$
    source-branches: []
    tracks-release-branches: true
    is-release-branch: false
    is-mainline: false
    pre-release-weight: 0
  main:
    mode: ContinuousDelivery
    tag: ''
    increment: Patch
    prevent-increment-of-merged-branch-version: true
    track-merge-target: false
    regex: ^master$|^main$
    source-branches:
    - develop
    - release
    tracks-release-branches: false
    is-release-branch: false
    is-mainline: true
    pre-release-weight: 55000
  release:
    mode: ContinuousDelivery
    tag: beta
    increment: None
    prevent-increment-of-merged-branch-version: true
    track-merge-target: false
    regex: ^releases?[/-]
    source-branches:
    - develop
    - main
    - support
    - release
    tracks-release-branches: false
    is-release-branch: true
    is-mainline: false
    pre-release-weight: 30000
  feature:
    mode: ContinuousDelivery
    tag: useBranchName
    increment: Inherit
    prevent-increment-of-merged-branch-version: false
    track-merge-target: false
    regex: ^features?[/-]
    source-branches:
    - develop
    - main
    - release
    - feature
    - support
    - hotfix
    tracks-release-branches: false
    is-release-branch: false
    is-mainline: false
    pre-release-weight: 30000
  pull-request:
    mode: ContinuousDelivery
    tag: PullRequest
    increment: Inherit
    prevent-increment-of-merged-branch-version: false
    tag-number-pattern: '[/-](?<number>\d+)'
    track-merge-target: false
    regex: ^(pull|pull\-requests|pr)[/-]
    source-branches:
    - develop
    - main
    - release
    - feature
    - support
    - hotfix
    tracks-release-branches: false
    is-release-branch: false
    is-mainline: false
    pre-release-weight: 30000
  hotfix:
    mode: ContinuousDelivery
    tag: beta
    increment: Patch
    prevent-increment-of-merged-branch-version: false
    track-merge-target: false
    regex: ^hotfix(es)?[/-]
    source-branches:
    - develop
    - main
    - support
    tracks-release-branches: false
    is-release-branch: false
    is-mainline: false
    pre-release-weight: 30000
  support:
    mode: ContinuousDelivery
    tag: ''
    increment: Patch
    prevent-increment-of-merged-branch-version: true
    track-merge-target: false
    regex: ^support[/-]
    source-branches:
    - main
    tracks-release-branches: false
    is-release-branch: false
    is-mainline: true
    pre-release-weight: 55000
ignore:
  sha: []
commit-date-format: yyyy-MM-dd
merge-message-formats: {}
update-build-number: true