User storage not saved between conversation but same user is recognized - actions-on-google

Question

In my Actions on Google project, I save some data (like an uuivd userId) between conversations using conv.user.storage. With my own testing account, this works fine. On another testing account, the user.storage is cleared and the data is lost. The accounts have these differences:
A Google Home is connected to the account where user storage DOES works and voice match is set up, personal results is enabled.
NO Google Home is connected to the account where user storage DOESN'T work, no voice match is set up, personal results isn't an option since no device other than iPhone is connected. This account is used on smartphone (iPhone) only.
I know the user storage will be cleared when:
Voice match is set up and there is no match.
The user disabled personal data.
But this isn't the case for either accounts. I know the user is recognized as the same account because of the lastSeen and because the userId between conversations remains the same, as can be seen in the Conv object:
at the end of the conversation:
"user": {
"raw": {
"userStorage": "{\"data\":{\"userId\":\"f581e751-ad81-4a6b-9519-00a57d5e30d4\"}}",
"lastSeen": "2019-03-13T11:58:39Z",
"locale": "nl-NL",
"userId": "ABwppHEOonglGmWakeizd_Stx_OpUhSNzx2K4JWETc73FW-KctZLM2vc4B7V6Fxk9OfL3RQ3n5jIgw"
},
"storage": {
"userId": "f581e751-ad81-4a6b-9519-00a57d5e30d4"
},
"_id": "ABwppHEOonglGmWakeizd_Stx_OpUhSNzx2K4JWETc73FW-KctZLM2vc4B7V6Fxk9OfL3RQ3n5jIgw",
"locale": "nl-NL",
"permissions": [],
"last": {
"seen": "2019-03-13T11:58:39.000Z"
},
"name": {},
"entitlements": [],
"access": {},
"profile": {}
},
at the beginning of a new conversation:
"user": {
"raw": {
"lastSeen": "2019-03-13T11:59:33Z",
"locale": "nl-NL",
"userId": "ABwppHEOonglGmWakeizd_Stx_OpUhSNzx2K4JWETc73FW-KctZLM2vc4B7V6Fxk9OfL3RQ3n5jIgw"
},
"storage": {},
"_id": "ABwppHEOonglGmWakeizd_Stx_OpUhSNzx2K4JWETc73FW-KctZLM2vc4B7V6Fxk9OfL3RQ3n5jIgw",
"locale": "nl-NL",
"permissions": [],
"last": {
"seen": "2019-03-13T11:59:33.000Z"
},
"name": {},
"entitlements": [],
"access": {},
"profile": {}
},
Does anyone know any other reason why user.storage might be cleared other than the ones stated above, or another way without using account linking?

Answer 1

I think I figured it out. In https://myaccount.google.com/u/3/activitycontrols?utm_source=google-account&utm_medium=web I forgot to toggle the Chrome-history and activity option.