Problem with RELATED function: "The column ither doesn't exist or doesn't have a relationship..."

Hello everyone,

I have the following problem:

I have two tables, one contains data about recruitment projects [Jobs] and the second one is a calendar [Calendar].

In the Calendar Table I have a Calculated column, which checks whether the date is in the current month (current indicates the last month of data from my data source) and returns different text depending on whether it is correct or no.

The code is below:

IsCurrentMonth = 
IF (
    AND (
        YEAR ('Calendar'[Date]) = YEAR ( [ReportingDate] );
        MONTH ('Calendar'[Date]) = MONTH(MAX(Jobs[Created Date]))
    );
    "Current Month";
    "Other"
)

I have a relationship between these two tables based on a date the project was created: Jobs[Created Date] and a date Column Calendar[Date].

I want to have another column in the Jobs table that checks whether the salary for the job was provided in the right format (it cannot be lower than 500) and I want this information to be available only for the current month (I cannot use filters on the visuals as there are other columns in the table tha present data for the whole year), so I used this code below.

MonthNoSalary =
AND (
    OR ( Jobs[Salary From] < 500; Jobs[Salary To] < 500 );
    RELATED ( 'Calendar'[IsCurrentMonth] ) = "Current Month"
)

It worked for some time but then I decided to change from columns in text format to TRUE/FALSE and then everything stopped working and I get the following message:

"The column 'Calendar[IsCurrentMonth]' either doesn't exist or doesn't have a relationship to any table available in the current context."

I tried to change it back to Text but it still doesn't work... And I have an older file where I did not change and everything works there.

I would be grateful for any help as I am running in circles...