The key reason the Budget entries fail to light up in the embedded PowerBI (Cash overview - current company & Cash overview - all companies) is primarily because the field value: MainAccount record is blank in table:LEDGERCOV. In order to solve this, make sure the Dependent account is setup against the nominal accounts used in your Budget register entries.
For example you wish to put a budget against two nominals (40000005 & 70020070) in the "Budget register entries"

Navigate to Main Accounts (nominal account: 40000005)/ Legal entity overrides --> Cash flow forecast and populate as follows

Navigate to Main Accounts (nominal account: 70020070)/ Legal entity overrides --> Cash flow forecast and populate as follows

The above changes will get reflected in the Cash flow forecast setup --> General ledger --> Dependent accounts as under

Run "Calculate cash flow forecast setup" with Total option
As a check if you have access to AxDB run the following query
select * from LEDGERCOV
where POSTING = 101
You should the records from Budget register entries populated as under (note: MainAccount field is populated with the RecID of Dependent account)

Go to Entity store and refresh the following measures
- LedgerCovLiquidityMeasurement
- BudgetActivityMeasure
- BudgetPlanActivityMeasure
- BudgetVsLedgerActivityMeasure
If you have access to DW you can run the following query after the above measures are refreshed
SELECT *
FROM [dbo].[LedgerCovLiquidityMeasurement_LedgerCovLiquidityEntity_MATERIALIZED]
where DOCUMENTTYPEENUSONLY like 'Budget register entry'
You should the records from Budget register entries populated as under:

Open the embedded PowerBI (Cash overview - current company & Cash overview - all companies) and you should see the budget entries light up in "Daily forecast summary". Note: I could not get the entries light up in the "Forecast details pane though.
