Plata je primljena bez obzira na radni odnos na određeno vreme.

This is a passive construction:

• je = is/has/was (from biti, to be)
• primljena = passive participle of primiti, to receive

So Plata je primljena literally means The salary has been/was received.

This kind of wording is common in formal or administrative Serbian, where the focus is on the result, not on the person who received it.

Because it agrees with plata, which is:

• feminine
• singular

So the participle must also be feminine singular:

• primljen = masculine singular
• primljena = feminine singular
• primljeno = neuter singular

Since plata is feminine, Serbian uses primljena.

It can mean either, depending on context.

Serbian often uses the same perfect form where English would choose between:

• was received
• has been received

So Plata je primljena may be translated either way. English makes a stronger distinction between those two tenses than Serbian usually does.

Bez obzira na is a fixed expression meaning regardless of or irrespective of.

It functions as a unit, so it is best to learn it as one chunk:

• bez obzira na + accusative = regardless of ...

In this sentence, it introduces the thing that does not affect the result.

Because bez obzira na takes the accusative, and radni odnos is a masculine inanimate noun.

For masculine inanimate nouns, the accusative singular is usually the same as the nominative singular. So:

• nominative: radni odnos
• accusative: radni odnos

That is why there is no visible change here.

This is a formal employment term.

• radni odnos = employment relationship / employment status
• na određeno vreme = for a fixed period, fixed-term, temporary

So radni odnos na određeno vreme means fixed-term employment.

A common contrast is:

• na određeno vreme = fixed-term
• na neodređeno vreme = indefinite / permanent / open-ended

Because they belong to two different expressions:

• bez obzira na = regardless of
• na određeno vreme = for a fixed period

So the sentence is not repeating the same structure by accident. Each na is part of a different grammatical unit.

Because na određeno vreme also uses the accusative, and vreme is a neuter singular noun.

For many neuter nouns, nominative and accusative singular look the same:

• nominative: određeno vreme
• accusative: određeno vreme

So again, the case changes grammatically, but there is no visible ending change.

Yes, it is understandable, but it sounds quite formal and compressed, almost administrative.

A fuller and clearer version could be:

Plata je primljena bez obzira na to što je radni odnos bio na određeno vreme.

That version makes the relationship more explicit: the salary was received even though the employment was fixed-term.

They describe the same event from different perspectives:

• primljena = received
• isplaćena = paid out

So:

• Plata je primljena focuses on the employee or recipient side.
• Plata je isplaćena focuses on the employer or payment side.

Both are possible in salary-related language, but they are not exactly the same in meaning.