Steps to reproduce:

* Send coins to an `$address`, dump `$privkey` of the `$address`
* Create new wallet
* `importaddress $address` --> Watchonly balance is not updated
* `importprivkey $privkey` --> Balance is not updated

Needs a restart to get fixed. See also #11477 
{
    if (data.exists("timestamp")) {
        const UniValue& timestamp = data["timestamp"];
        if (timestamp.isNum()) {
            return timestamp.getInt<int64_t>();
        } else if (timestamp.isStr() && timestamp.get_str() == "now") {
            return now;
        }
        throw JSONRPCError(RPC_TYPE_ERROR, strprintf("Expected number or \"now\" timestamp value for key. got type %s", uvTypeName(timestamp.type())));
    }
    throw JSONRPCError(RPC_TYPE_ERROR, "Missing required timestamp field for key");
}
RPCHelpMan importmulti()