محاولة تسجيل الدخول اليوم.

It is most naturally understood as a noun phrase, not a full verb sentence.

Arabic often uses short noun phrases in:

• app and website interfaces
• notifications
• headlines
• labels

So this can work like Login attempt today or Attempt to log in today in a system message.

If you wanted a full sentence, you could say things like:

• تمت محاولة تسجيل الدخول اليوم = A login attempt was made today
• حدثت محاولة تسجيل الدخول اليوم = A login attempt occurred today

محاولة means attempt or trying.

Grammatically, it is a verbal noun (also called a maṣdar) from the verb حاول = to try / to attempt.

So:

• حاول = he tried
• محاولة = attempt / trying

In this phrase, محاولة is the main noun at the start of the expression.

Because Arabic often expresses ideas like attempt to do X with nouns, especially in formal writing and interface language.

So instead of a full verbal sentence, Arabic can use:

• محاولة تسجيل الدخول = attempt to log in

This is similar to English phrases like:

• login attempt
• attempted login
• attempt to sign in

So the lack of a verb is normal here.

It is an iḍāfa construction, often called a construct phrase.

The structure is:

• محاولة = attempt
• تسجيل = registering / logging
• الدخول = entry / entering

Together:

• محاولة تسجيل الدخول = literally attempt of logging in
• more naturally: attempt to log in

Arabic often uses this noun-based structure where English would use to + verb.

So instead of:

• attempt to log in

Arabic uses:

• attempt + logging in

This is because of the iḍāfa structure.

In an iḍāfa:

• the first noun normally does not take الـ
• the first noun also does not take tanwīn
• the last noun can be definite with الـ

Here the phrase is really a chain:

• محاولةِ / محاولةُ ...
• تسجيلِ ...
• الدخولِ

So:

• تسجيل is the first part of تسجيل الدخول
• محاولة is the first part of محاولة تسجيل الدخول

That is why محاولة and تسجيل appear without الـ, while الدخول can take it.

In Modern Standard Arabic, تسجيل الدخول is a very common fixed expression in technology and administration.

It usually means:

• log in
• sign in

So even though the words can be understood literally, learners should recognize the whole phrase as a standard tech expression.

Related examples:

• تسجيل الدخول = log in / sign in
• تسجيل الخروج = log out / sign out

Because د is a sun letter.

When الـ comes before a sun letter, the l sound assimilates to the next consonant.

So:

• الدخول is written al-dukhūl
• but pronounced ad-dukhūl

This is a pronunciation rule only; the spelling does not change.

Because اليوم here functions as an adverb of time: today.

In Arabic, time words often appear without a preposition:

• اليوم = today
• أمس = yesterday
• غدًا = tomorrow

So:

• محاولة تسجيل الدخول اليوم = login attempt today / attempt to log in today

You do not need في here.

Using في would usually change the feel or meaning:

• في هذا اليوم = on this day
• في اليوم can mean something like during the day or depend on context

Here it is pronounced with a t sound in connected speech:

• muḥāwalat tasjīl...

That happens because محاولة is in an iḍāfa and is followed directly by another noun.

So:

• alone, in pause: muḥāwala
• in this phrase: muḥāwalat tasjīl

This is a very common rule with ة:

• when a word is isolated, it often sounds like -a
• when grammatically connected, it can sound like -t

A possible fully vocalized reading is:

مُحاوَلَةُ تَسجيلِ الدُّخولِ اليَومَ

But there is an important detail: because this phrase is standing alone, the exact final case endings depend on the larger sentence it comes from.

In everyday writing, especially in apps or notifications, those short vowel endings are usually not written and usually not pronounced fully.

A practical pronunciation is roughly:

muḥāwalat tasjīl ad-dukhūl al-yawm

In very careful formal reading with case endings, the endings may be pronounced more fully.

Yes, you could.

Both are possible:

• محاولة تسجيل الدخول اليوم
• محاولة لتسجيل الدخول اليوم

The version without لِـ is:

• shorter
• more compact
• very common in formal writing, headlines, and interface text

The version with لِـ can sound a little more explicit, like:

• an attempt for the purpose of logging in

So the original phrasing is very natural, especially in a technical or system-message context.