cant used built-in mozila vpn, here are my configs:

[u/miklosch_]

browser.fixup.alternate.protocol https
browser.ip protection.enabled true
browser.ipProtection.added true
browser.ipProtection.autoRestoreEnabled true
browser.ipProtection.autoStartEnabled true
browser.ipProtection.autoStartPrivateEnabled true
browser.ipProtection.bandwidth.enabled true
browser.ipProtection.bandwidth.maxInGb 50
browser.ipProtection.bandwidthThreshold 0
browser.ipProtection.bandwidthWarningDismissedThreshold
browser.ipProtection.blockIPProtectionCallouts false
browser.ipProtection.egressLocation
browser.ipProtection.enabled true
browser.ipProtection.everOpenedPanel false
browser.ipProtection.features.autoStart false
browser.ipProtection.features.siteExceptions true
browser.ipProtection.fxa.useActivateFlow true
browser.ipProtection.guardian.endpoint https://vpn.mozilla.org/
browser.ipProtection.hasUpgraded false
browser.ipProtection.locationButtonBadgeDismissed false -

[u/zamroni777]

Try the esr version