Firefox 'cannot establish secure connection' to firebase hosting -

i have hosted website using firebase hosting, handfull of customers complain browser (i know 1 mozilla) gives message cannot establish secure connection, , not loads page.

it site: https://mad-science-aanmeldingen.firebaseapp.com/zuid-holland

it uses rewrite /index.html url bit different page loaded, seems firebase feature.

firebase hosting config:

{   "database": {     "rules": "database.rules.json"   },   "hosting": {     "public": "inschrijvingen",     "rewrites": [{       "source": "**",       "destination": "/index.html"   }]   } }